US2218133A - Manufacture of turbine oils - Google Patents

Description

Oct. 15, 1940. I LIOVELL 2,218,133

MANUFACTURE OF TURBINE OILS Filed Feb. 6, 1959 Fmdiondi'or V 78 Percolahnq Fil'her Propane lnvenror: Lawrence L. Lovell Patented Oct. 15, 1940 UNITED STATES PATENT orrlca MANUFACTURE OF TURBINE OILS Lawrence L. Lovell, Wood River, 111., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application February 6, 1939, Serial No. 254,827

10 Claims.

This invention deals with a method for producing hydrocarbon oils, such as light lubricating oils, and which are highly resistant to sludge formation, and more particularly is concerned with the manufacture of turbine oils by a method involving known steps and requiring nothing more than conventional petroleum refining equipment, whereby satisfactory turbine'oils may be produced from stocks heretofore considered more m or less unsuitable for this purpose.

It is a purpose of my invention to produce a stable oils suitable as turbine oils, transformer oils, spray oils, medicinal oils, etc. It is another purpose to produce such oils by steps requiring conventional treating equipment. It is another purpose to treat hydrocarbon oils with sulfuric acid and neutralize them without the use of caustic alkali or' contact clays or both; and it is a further purpose to produce acid treated oils free from objectionable sulfuric acid reaction products which are frequently left in the oil by the conventional methods of neutralization. It is well known that turbine oils must be more resistant to sludge formation by the action I of which they come in contact during use than any other type of-lubricating oils. Sludge inter-- duced oils with very bad emulsion properties after aging, and, in fact, itwas believed by many I that solvent extraction was more harmful than useful in thismatter. Now,- however;I have dis.-

covered that by subjecting a solvent raiiinate of proper viscosity range obtained by extraction with a naphthenic solvent from aMid Continent lubricating distillate oil to a series of simple treatments, highly satisfactory turbine oils 'can be obtained. While my method of treating appears to be particularly useful when applied to Mid-Continent raflinates, it is, however, not limited thereto, but is applicable as well to raflin-ates from other sources as, for example, from Pennsylvania, Gulf Coast, California, Rumania, Co-

, lombia, etc., oils.

- The solvent extraction should preferably be ing asphaltenes, resinsand the like from the oil.

This treatment may comprise or consist of distillation, propane precipitation, Pilat treatment, etc. It may precede or follow, or, as. in the.

case of the Duosol process, may be carried out air and water in the presence of the metals with.

accompanied by a treatment capable of removsimultaneously with the solvent extraction. If necessary, the oil may also be dewaxed at one stage or another, as convenience may direct.

.The rafiinate which is substantially free from asphaltenes and preferably free from wax, and having a preferred Saybolt Universal viscosity at 100 F. of about 100 to 200 seconds is treated at a normal temperature, i. e., at about 50 to 140 F. with concentrated sulfuric acid.

.About 5 to 20 pounds per barrel of sulfuric acid-having a concentration of 93% to 100%, and preferably 95% to 99%, is used advantageously. This treatment may be carried out in batch or continuously, and any conventional -means for mixing, such as air blowing or-mechanical mixing, are applicable. The oil so treated is allowed I to, settle, and insoluble sludge is removed as completely as possible. A small amount of water, e. g., about /8 to 2 per cent may be added to the sour oil tohydrolize the soluble sludge and to effect precipitation of suspended pepper'sludge. Additional sludge, which is thereby settled, is re-' moved. I

Instead of removing soluble sludge by hydrolysis with water, it may be-extracted with suitable solvents such as methyl or ethyl alcohol, acetone, etc. In the course of this treatment, whether it be hydrolysis or extraction, the color of the oil is materially improved.

The sludge-free oil which still contains dis-. solved S02 is blown with air or other convenient gas which is substantially chemically inert under .the conditions of this blowing, such as CO2, flue gas, nitrogen, hydrogen,etc., at an elevated tem-. perature below 200 F., e.'g., preferably between .about 'l50l90 F. to drive off the dissolved S02. TheSOz should be removed substantially completely, and this blowing treatment should be continued until a sampleof the oil tested shows a negative reaction for S02. S02, if allowed to remain in the oil'at thisstage, will promote side reactions. in the next following step and induce the formation of oxidized substances, which may have a detrimental effecton the qualities of the finished turbine oil. It is further of importance that in the S02 removal step the temperature be 1 kept below about 200 F. because at higher temperatures undesirable side reactions may and frequently do take place.

After the last traces of son have been elimi may settle out uponstanding. The time rebe polymerization products of unstable components in the oil, may vary from about one to two hours at 300 F. to two to three days at 220* quired to form these solids, which I believe to F. At 250-270 F., normally between about 8 to hours of air blowing are required. At temperatures below 220 F., the polymerization normally remains incomplete, no matter how long blowing is continued, and at temperatures above 300 F. undesirable oxidation reactions make themselves felt.

Instead of air, other oxygen-containing gases, such as pure oxygen, or non-oxidizing gases, may be used. However, if non-oxidizing gases are used, the polymerization proceeds very slowly and often remains incomplete.

The suspended solids in the blown oil are so finely divided that they cannot be removed completely by settling. Moreover, frequently colored substances are formed in the high temperature blowing which are soluble in the oil and which must be removed by means other than settling. I have found that both the suspended and dissolved harmful impurities contained in the oil after this stage may be removed by simple percolation, preferably at a temperature below about 100 F., of the oil through a suitable, active,

preferably naturally active, percolation clay such shown.

as Florida clay, Attapulgas clay, fullers earth, etc. operation, although coarser or finer clay may be used if desired. The oil resulting from the percolation has a light color and has the stability which is required of turbine oils. If desired, activated clays may be used, although I prefer naturally active clays.

The chemistry involved in the air blowing at the temperatures between 220-ilil F. is not well understood. In particidar, it is difiieult to explain why unextracted mineral oils such as ordinary Mid-Continent distillates normally yield relatively dark oils of poor stability when treated as above, and that treatment with excessive amounts of clay does not substantially improve their stability. Further, I have found that elimination of all the insoluble acid sludge prior to the high temperature air blowing at 220-300 F, as well as at least a major portion of the soluble sludge together with dissolved S02 is essential. It is, however, relatively immaterial by what means this is accomplished. For example, I may treat the acid treated acidic oil, which has been i'reed from insoluble sludge but which contains small amounts of dissolved sludge, with liquid water at a temperature above 212 F. and under superatmospheric pressure, if desired, in the presence of an amount of a base such as caustic soda, lime, aqueous ammonia, etc. However, I do prefer the method hereinbefore described, of hydrolyzing with water at normal pressure, settling additional sludge formed thereby and eliminating $02 by blowing attemperatures below 200 F. This method is simple, eflective, inexpensive and consumes no chemicals other than air and water.

My invention will be more fully understood from the accompanying drawing which represents a flow diagram of a preferred form of my process. Topped mineral crude oil containing lubricating fractions substantially free from gasoil and lighter components enters extractor l near its bottom through line 2 from a source not Propane is simultaneously injected through line 3. Anaphthenic solvent, such as liquid S02, furfural, phenol, cre'sylic acid, betabeta-dichlorethyl ether, etc., is introduced into the top of the extractor I through line 4. The propane solution and naphthenic solvent flow countercurrently through the extractor I, extract I prefer to use a 30/60 mesh clay for this the bottom of the extractor through line 5,-and

rafiinate-propane solution flowing through line 8 to heater '1 and column 8 where propane containing traces of naphthenic solvent is flashed off. Rafilnate free of solvent is conducted through heater 9 in line l0 to fractionating column II where a light lubricating distillate having preferably a Saybolt Universal viscosity at 100 F. of 150 to 160 seconds is takenoverhead through line l2, residue being withdrawn through bottom line IS. The distillate vapors in line l2 are condensed in condenser l4 and condensate is stored in tank i5.

Lubricating distillate is conveyed from tank it by pump iii in line ill to agitator iii, which is equipped with steam heating coil l9, sludge line 20, air line 2i and lines 22 and 23 for introducing concentrated sulfuric acid and water, respectively. When the agitator has been filled with rafiinate distillate oil to the desired level and the temperature has been adjusted to between 50 and 140 F., the proper amount of sulfuric acid is dumped into it. Air is then admitted through line 2! to provide the necessary agitation, and after sludge has been formed, the air current is turned off and sludge is allowed to settle and is withdrawn through line fill. A small amount of water is now introduced into the. oil through line .23 and is agitated with the oil to efiect removal of the suspended pepper sludge and hydrolysis of the dissolved sludge. The secondary sludge so formed is settled and drawn through line 2b. The oil which is now substantially sludge-free but contains dissolved S02 is heated by means of 3 coil ill to a temperature preferably between 150 and 190 F. At this temperature, air is blown through the oil to remove the dissolved S02. When this has been accomplished, the temperature of the charge in the agitator is further raised .to about 250-270 while air blowing is continued for about 8-20 hours. During this period, the oil turns dark purple. Without allowing coloring material to settle, the dark oil is cooled, is withdrawn from the agitator through line 2d and is'conveyed by pump 25, preferably at a temperature below about 100 F. through percolation filter 26-whioh is filled with a suitable active bleaching clay such as fullers earth. The percolated oil, which is very bright and of light color, goes through line 21 to storage tank 28.

The clay, which has been spent by contact with the oil treated as described, can be revivified by burning in the conventional manner.

While in the above I have described a simplifled flow diagram of my process, it is understood that many modifications within the scope of my invention are possible. For example, the differout treatments carried out in the single agitator of pumps wherever required is considered within the skill of the designer for refinery requipment.

The following example further serves to illustrate my process:

A lead lined agitator was charged with 743 barrels of a lubricating oil rafllnate distillate having a Saybolt Universal viscosity at F. of seconds, obtained from a Mid-Continent crude by extraction by the Duosol process.-- The charge was treated at 80 F. with 10.1 pounds per barrel 98% sulfuric acid. The resulting mixture was air agitated for 50 minutes and the sludge was allowed to settle and was drawn ofi. 0.75% water was then added to the sour oil and the agitation was resumed for 30 minutes at 80 F. to effect hydrolysis of dissolved sludge. The hydrolyzed oil was settled-and an asphaltic sludge was drawn 011. The oil was then passed through a heat exchanger into another lead lined agitator. The temperature of the oil after transferring was 150 F., and at this temperature the oil was blown with air free of S02.

After the removal of the S02, the oil was circulated through the heat exchanger until the temperature reached 240 F. During the heating, a small amount of air was blown through the oil to remove the excess moisture and to insure mixing. When the temperature reached 240 F. the air was increased until violent agitation was attained. The polymerization of unstable constituents was effected by blowing for 14 hours with air between the temperatures of 250 and 270 F. The polymerized oil was then allowed to cool and was percolated through fullers earth at a temperature slightly below 100 F. The following data were obtained:

Some of the more important properties of the treated oil in comparison with the properties of a turbine oil produced by conventional sulfuric acid treatment followed by contact neutralization with clay were as follows:

011 properties New ttiiilrbine caiirvfiggigfial Gravity, A. I. I 31.6 31.2. Color- 19 Say 1 +NPA. Demulsification at 130 F 1620 1620. Emulsion test-NaOH at 130 F 1 minute 4 minutes. Steam emulsion number 30 60. RL emulsion test Initial emulsion No emulsion 900. Emulsion after 1 hour's aging--- 1000 280. Emulsion after 6 hours aging 276 180. Original interiacial tension, 38.9 37.7.

dynes/eentimeter. Interracial tension after 1 hours 27.8 24.8.

flgmglntgirfacial tension after 6 hours 20.4 19.0.

a 11g. Swiss turbine oil aging test Steam jet test RL emulsion alter aging Interiacial tension after aging Sludge nig./200 m 6 Acid number Saponiiication number I For description of the RL emulsion test, see the Institute of Mechanical EngineerPGeneral Discussion on Lubrication and Lubricants Group IV Properties and Testing," October 1937, pps.

The Swiss turbine oil test is described in Schweizerischer-Verband iiir die Matarialpriiiung'en der Technik SVMT 17, July 12,

If desired,oxidatiori or corrosion inhibitors such as phenyl alpha naphthylamine, aromatic sulfur compounds, etc., may be added to the oils treated by my process further to increase their resistance against the sludge inducing influence of metals.

I claim as my invention:

1. In the process of producing stable hydrocarbon oils suitable for lubrication, the steps comprising treating a lubricating rafllnate obtained by extracting a hydrocarbon oil with a naphthenic solvent which is substantially free of asphalt and resins with an amount of concentrated sulfuric acid suflicient to produce sludge and S02, separating the sludge-to produce a substantially sludge-free oil containing S02, blowing the resulting sour oil with a gas which is substantially chemically inert under the conditions of the blowing to remove further blowing the resulting S02-free oil with an oxygen containing gas at a temperature between 220 and. -800-? F. for a time suflicient only to substantialiy effect polymerization of unstable components of the lubricating oil, whereby the color of the oil is materially darkened, and contacting the darkened oil with an active bleaching clay to decolorize the oil.

2. 1n the process of producing turbine oils, the steps comprising treating a lubricating rafiinate obtained by extracting a hydrocarbon oil with a naphthenic solvent which is substantially free of asphalt and resins and has a. viscosity suitable for turbine oils with an amount of concentrated sulfuric acid suificient to produce sludge and S02, separating the sludge to produce a substantially sludge-free 011 containing S02, blowing the resulting sour oil with a gas which is substan-' tially chemically inert under the conditions of the blowing to remove S02, further blowing the resulting SOs-free oil with an oxygen containing gas at a. temperature between 220 and 300 F. for a time suflicient only to substantially effect polymerization of unstable components of the lubricating oil, whereby the color of the oil is materially darkened, and contacting the darkened oil with an active bleaching clay to decolorize the oil, i

3. The process of claim 1 in which the oil is a distillate oil.

4. The process of claim 2 in which the oil has a Saybolt Universal viscosity at 100 F. of 100-200 seconds.

5. In the process of producing a turbine oil, thesteps comprising treating a lubricating raffinate .distillate obtained by extracting a hydrocarbon oil with a naphthenic solvent having a viscosity suitable forturbine oils with 5 to 20 pounds concentrated sulfuric acid at a temperature between 50-140 F., thereby producing soluble and insoluble sludge and S02, separating the insoluble sludge, treating the resulting sour 011 containing dissolved sludge and S0: with a small amount of liquid water to hydrolyze soluble sludge, thereby precipitating same, separating the hydrolyzed sludge, blowing the sludge-free oil containing dissolved S02 with air at a temperature below 200 F. to remove S02, further blowingthe SOs-free oil with air at a temperature between 220-300 F. for a time only suflicient to substantially polymerize unstable components of the oil whereby the color of the oil is darkened, and contacting the darkened oil with an active clay at a temperature below 100 F.

6. The process of claim 5 inwhich the sulfuric acid has a concentration of -100%,

7. The process of claim 5 in which the amount of water is to 2% of the oil.

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