US2276526A - Process for refining hydrocarbon oils - Google Patents

Description

G. H. voN FucHs E-rAL PROCESS FOR REFINING HYDROCARBON OILS March 17, 1942'.

Filed April 5, 1959 whh Cuprous Oxide Ef1ecf of Trre and Terr permre an S Remool Time, Mnues Flq l Solvenr 8 Dslhnq Column Sfeom Gm r mm 0d am .ma 44mm e I V Al.. I. o W. o w uJ n m5 M 2 s a m, O QL 9 Nophenic Solvenr Exhodon Hydrocarbon Oil CUS lnvenrorszGeorge Hugo Von Fuchs Patented Mar. 17, 1942 .v

LUNITED STATES PATENToF-Flca PROCESS Foa REFzLnG nYDaocARBoN George Hugo von Fuchs, Wood River, and Hilbert Harry Zuidema, Edwardsville, Ill., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application April 3, 1939, Serial No. 265,650

' (cl. 19e-3o) Claims.

treated by our process have particularly good stability in the presence of metallic copper. Another object is to remove mercaptan sulfur without converting it to disulfide sulfur. Still another object is to reduce disulfide sulfur a1- ready contained in the oil to mercaptans and removing the mercaptans so formed.

Broadly, our process comprises treating the lubricating oils free from asphalt in the liquid state preferably at about 500 to 600 F. with cuprous oxide substantially free from cupric ,a

oxide to convert the mercaptans to cuprous sulfide which is insoluble in the lubricating oil,

and then removing the cuprous sulfide from the oil in any suitable manner.

Our process is preferably applied to lubricating raflinates obtained by extraction with a suitable so-called naphthenic solventi. e. which preferentially dissolves aromatic hydrocarbons from mixtures comprising parains and aromatics, and is followed advantageously by treatment with H2SO4.

vLubricating oils which have received no oxidation treatment normally contain varying amounts of mercaptans but usually are substantially free from disulfides. It is generally known that mercaptans are harmful and for this and other reasons oxidation treatments capable of converting mercaptans to disulfldes are frequently employed. Such treatment may comprise the.conventional H2504 and Doctor treatments, oxidation with air, etc. Now, however, We have found that disulfides as well as mercaptans are harmful in regard to sludge formation in electrical equipment. One of the tests which we have used for the determination of sludge forming tendencies in oils used in electrical equipment consists of heating a sample of an oil at 302 F. for 8. hours -in the presence of copper. The oil is observed for color and sludge before and after the eect of disulfide Vsulfur in small quantities on the formation of 4sludge and darkening of the g TABLE I 8 hour test at 302 F. in the presence of copper Percent disulde sulfur Sample N. P. A. color after test 4% (no sludge).

1 (no sludge).

5 (trace of sludge).

4 (considerable sludge). 6 (considerable sludge).

Disuldes form sludge in the presence of copper neven at lower temperatures, e. g. 203 F. when Percent disulfide sulfur Sample Appearance alter test No sludge. Trace of sludge; 1 Sludge.

According to these data the maximum disulfide sulfur content that may be tolerated is of the 'order of .015% calculated as sulfur and prefer- The mercaptans formed in Equation 2 yreact with more cuprous oxide so that all of the mercaptans are eventually converted to cuprous sulfide and olens.- provided that at least one mol of cuprous oxide is used in the treatment for every mol of mercaptans contained in the oil. Disulfides may also be removed with cuprous oxide provided that the temperature ofthe treatment is high enough to cause thermal decomposition of the disuldes into more reactive compounds -such as mercaptans. For complete thermal decomposition of disulfdes, temperatures as high the test. The following experimental data show as 600 F. may be required.

F. in the presence of copperv this limit.

A complete removal of mercaptans or disuldes is not always necessary as it has been found that about 0.01% of mercaptan sulfur may be tolerated in the finished oil therefore slightly less than one mol of CuaO per mol of mercaptans actually or potentially present may be sufficient to reduce the sulfur content enough to produce a nonsludging oil. However, the amount of CuaO should be suillcient to reduce the harmful sulfur to a point not to exceed 0.01%. In general, we prefer to use between 1 and 2 mols of'CuzO per mol of potential mercaptan sulfur. By harmful sulfur or mercaptan sulfur potentially present we mean the mercaptan sulfur actually present and that which may be liberated by decomposition of Since, as is shown in Table I and Ia, disulfldes are harmful, it is essential that conditions leading to the formation of them be avoided. 'Ihus substances capable of converting mercaptans to disulfldes under the conditions of the treatment should be absent.

For example, there should not be substantial amounts of air present or easily reducible metal oxides such as CuO, FezOa. Ninos, etc. A' cuprous oxide therefore must be employed which contains as low as possible an amount of cupric oxide, cupric oxide being the most common impurity of commercial cuprous oxide, for cupric oxide reacts under the conditions of the treatment with mercaptans according to the reaction:

yielding the objectionable disulfide.

The following data show the effects of cuprous oxides` containing different amounts of cupric oxide.

Since as previously pointed out, the maximum permissible disulfide s ulfur content in the treated oil is below .015% the maximum permissible con, tent of cupric oxide in the cuprous oxide is limited to that which yields disulfide sulfur below This maximum will vary with the amount of cuprous oxide used in the treatment. The more cuprous oxide required, the less the tolerance for cupric oxide. In general we prefer cuprous oxide which contains less than 10% and preferably less than 5% cupric oxide. We have found that such a cuprous oxide isv normally satisfactory and generally has a bright red color as distinguished from brown or brown red cuprous oxide. 'As may be seen from the following analysis' bright red cuprous oxides normally contain less than 5% cupric oxide whereas brown red contains about or more.

. AAppearance Cu() Per gt4 B h 3.5 do B 16.5

'I'he cuprous oxidemay be added to the lubricating distillate to be. treated in the dry state or in the form of an oil slurry. Contact may be maintained for the necessary length of time by mechanical agitation or by passing a gasA free from free or easily available oxygenthrough the mixture such as steam, nitrogen, hydrogen, etc. The operative temperature range is between 400 F. to'700 F., and as CuzO at high temperatures in the neighborhood of 700 F. may induce cracking, we prefer to limit the time in this temperature range so as to avoid substantial production of olenes. Oleflnes, as is well known, adversely affect the stability of hydrocarbon oils. At about 700 F. desulfurization is usually accomplished in a few seconds and it is therefore possible to operate in this temperature range of lincipient cracking without danger of the formation of ex- `cessive amounts of oleflnes, however, because of this possibility of cracking, the maximum temperature should be substantially below 700 F. unless the contact time is very short. At temperatures below 400 F. mercaptan sulfur is converted too slowly and incompletely to be of practical value. Temperatures between 450 F. and 600 F. and preferably between 500 F. and 570 F. being particularly useful. 'I'he effect of time and temperature is illustrated in Figure I of the attached drawing which represents the actual removal of mercaptans by our process with time i at various temperatures, the of mercaptan sulfur and disulfide sulfur left after the treatment being plotted against time for several temperatures. The abscissae in Figure I represents the time required to remove the sulfur compounds after the temperatures in question were reached.

As will be seen substantially complete removal of mercaptans can be achieved at 500 F. in about 30 minutes-or in about 5 minutes at 570 F. without substantial formation'of disulildes.

After completion of the above treatment, the cuprous sulfide formed in the process must be removed together with the excess of cuprous oxide. This may be done by settling, filtration or other 4conventional methods.

Since olens are formed and soluble copper compounds and undesirable compounds may result from the reaction or may have been introduced from an outside source, the cuprous oxide treatment of the hydrocarbon oil vshould be followed by a conventional sulfuric acid treatment. Such a treatment comprises adding 10 to 50 lbs. of sulfuric'acid of 90 to 100%, preferably 93 to 98% concentration, per barrel of hydrocarbon oil to be treated and lagitating, if desired, with air. Acid components from the treatment may be removed by conventional means such asneutralization with aqueous caustic soda, alcoholic caustic soda, pressure hydrolysis, contact clay treatment, etc., and in addition the oil may be further refined by percolation through a naturally active clay such as Florida, Attapulgus and Ohmstead clays, Instead of removing oleflns by acid treatment they may be removed or be converted to nonsludging compounds by other known means such as hydrogenation.

able naphthenic solvent.

oxide and thus increase the amount of cuprous oxide required for removing mercaptans.

Referring now to Figure 2 of the attached drawing which represents a flow diagram of a preferred form of our process. A hydrocarbon oil free from asphalt is passed through line I into extractor 2, where the oil is separated into a raffinate and extract by extraction with a suit- An extract layer is drawnoff through line 3 and the rafiinate is taken overhead through line 4, picked 4up by pump 5 and pumped through heater 6 into fractionating column 1 where the rafiinate is freed of solvent by fractional distillation. The solvent about 5 to 30 minutes. The oil may be agitated selected from the group consisting of lubricating and electrical oils free from asphalt containing harmful sulfur in the form-of mercaptan sulfur, the steps comprising heating said oil in the liquid state at a temperature from about 400 F. to '100 F..with at least 1 mol cuprous oxide per mol of said mercaptans under non-oxidizing condiv tions to convert mercaptan sulfur to cuprous sulfide and substantially to prevent conversion of by steam from line I5 and/or by mechanical agitator I6 during the heating to insure thorough contact with the CuzO. At the end of the necessary time the CuzO treated oil is withdrawn by pump I8 through valve I2 and line II and is forced through filter I9 to remove the cuprous sulfide and excess cuprous oxide. The cuprous sulfide and excess cuprous oxide are discharged through discharge line 20 and the filtrate passes through line 2l into agitator 22. In this agitator about 10 to 50 ibs. per barrel of concentrated H2SO4 are added to the hydrocarbon oil by way of line 23 and the mixture agitated by air from line 24.- This treatment removes the unsaturates, and also 'soluble copper compounds and traces of solvent if present, in the form of a sludge which settles and may be removed through discharge 25. The treated oil is conveyed by pump 26 through line 21 into which NaOH is fed from line 28 in quantities sufficient to neutralize the oil. The neutralized oil now passes into separator 29 and sludge settles out and is removed by Way of line 30. 'Ihe refined oil is now ready for use, but if desired it may be further refined by passing it through line 3| and clay percolator 32A and thence through line 33 to storage.

The following example further illustrates. our process.

A raffinate, obtained by extracting a West taining mercaptans was heated at 500 F. for

one-half hour with .5% by weight of a bright red cuprous oxide using steam for agitation. The mercaptan sulfur was converted to cuprous suide which along with the excess cuprous oxide' was filtered oi. Analysis of the filtrate showed no measurable quantity of mercaptan or disulfide sulfur, showing that the reaction with the cuprous oxidewas quantitative. This oil was acid treated with 50 lbs. per barrel of 98% H2SO4, neutralized with aqueous NaOH and was percoiated through percolation clay. The resulting oil having the properties of a transformer oil was subjectedto the before described test at 302 F. in thev presence of copper. No sludge was formed.

We claim as our invention: Y

1. In the process of refining a hydrocarbon oil mercaptans to disulfides. y 2. Process of claim l in which the hydrocarbon oil is a bright stock.

3. Process of claim 1 in which the hydrocarbon oil is raffinate obtained by extracting minl eral oil with a naphthenic solvent.

4. In the process of refining a hydrocarbon oii selected from the group consisting of lubricating and electrical oils free -from asphalt containing harmful sulfur in the form of mercaptan and disulde sulfur, the steps comprising. heating said oil in the liquid state at a temperature above 400 F. and below cracking temperature, and under non-oxidizing conditions with at least 1 moi of a bright red cuprous oxide per mol of said mercaptans under conditions to convert mercaptan sulfur tocuprous sulfide and removing the cuprous sulfide s0 formed.

5. In the process of refining a hydrocarbon oil,

selected from the group consisting of lubricating and electrical oils, and free from asphalt and containing sulfur in the form of mercaptan sulfur, the steps comprising heating said oil in the liquid state from about 450 F. to 600 F. under nonoxidizing conditions in the presence of at least 1 i. mol of a. cuprous oxide substantially free from readily reducible metallic oxides per mol of said mercaptans under conditions to convert mercaptan sulfur to cuprous sulfide and removing the cuprous sulfide so formed.

6. In the process of refining a hydrocarbon oil selected from the group consisting of lubricating and electrical oils free from asphalt and containing harmful sulfur in the form of mercaptan fsulfur, the steps comprising heating said oil in the liquid state at a. temperature from about 500 F. to 570 F. under non-oxidizing conditions in the presence of at least one mol per mol of said mercaptans of a cuprous oxide containing less than 10% cupric oxide for a time sufficient substantially completely to convert the sulfur of said mercaptans to cuprous sulfide and separating the cuprous sulfide so formed.

'7. In the process of refining a rafiinate selected from the group consisting of lubricating and electrical oils, obtained by extracting a minerai oil with a naphthenic solvent, said raffinate containing harmful sulfur in the form of mercaptan and disulfide sulfur and being free from asphalt, the steps comprising heatingsaid raffinate in the liquid state at a temperature from about 400 F. to 700 F. under non-oxidizing conditions in the presence of at least 1 mol of a bright red cuprous oxide per mol of said'mercaptans for a time sufficient to convert said mercaptans to cuprous sulfide and oleflns, separating the cuprous sulfide and removing the olenes from the resulting oil.

8. In the process of 4 refining a rainate obtained by extracting a lubricating oil with a naphthenic solvent which raffinate is free from asphalt and contains harmful sulfur in the form of mercaptan sulfur, the steps comprising heating said raffinate in the liquid state at a temper- .ature of 400 F. to '700 F. under non-oxidizing tainng not more than 10%l cupric oxide for a time suicient to substantially completely convert saidmercaptans to cuprous sulflde and ole- .ns separating the cuprous sulflde,v subjecting the resulting oil free from CuzzS to a treatment with concentrated sulfuric acid and neutralizing the acid treated oil.

9. In the process of producing an oil for electrical purposes which is non-sludging when subjected to an 8 hour test at 302 F. in the presence of copper, the steps comprising treating a raffinate produced by .extracting a mineral oil with a naphthenic solvent, said ratilnate having a viscosity suitable fo'ran electrical oil, containing harmful sulfur in the form of mercaptan and disulde sulfur, and being free from asphalt, by heating in theliquid state with at least 1 mol of a bright red cuprous oxide per mol of mercaptans in said rafiinate at a temperature of l450 F. to 600 F. under non-oxidizing conditions for a time sufiicient to convert substantially all of said mercapt'ans to cuprous sulfide and olens, separating the cuprous sulde so formed and unreacted cuprous oxide, subjecting the resulting oil to a treatment with 10 to 50 lbs. per barrel of sulfuric acid having a concentration of 95-98%, neutralizing the acid treated oil and percolating the neutralized oil through a bed of percolation clay.

10. In the process of rening a hydrocarbon oil selected from the group consisting of lubricating and electrical oils free from asphalt containing harmful sulfur in the form of disulfide sulfur, the steps comprising heating said oil in the liquid state to a temperaturesulciently high to convert disuldes to mercaptans and treating the heated oil at a temperature of about 400 F. to

700 E. with at least 1 mol of cuprous oxide per mol of said harmful sulfur under non-oxidizing conditions to convert mercaptans to cuprous sulde and substantially to prevent conversion of mercaptans to disulfldes.

GEORGE HUGO voN FUCHS. HILBERT HARRY ZUIDEMA.

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