US2266359A - Treatment of petroleum oils - Google Patents

Description

Dec. 16, 19.41. T. o. EDWARDS. JR.. ETAL 2,266,359

TREATMENT OF PETROLEUM OILS Filed May 9, 1938 TO VA CUUM PUMP if, ar i w /4 f\ 20 1 K L.

HEA TER a: TT'L ING I N VENTORS CHAMBER A TTcSR/vEY.

1 plates of; the tower. 'amounts -vofhalkali results in an increas in the :zcorrosiondifflculties encountered asiwell as an increasein the amountaof alkali'entralned by the 'cvapors andl carried upward in the tower. maintenance ofa high reflux on the lower plates Patented Dec. 16, 1941 .mmrmr'or rmqmmoms V j -Thomas Oliver; In, andOscai-Y Larson, i

'Associa' ted, "califwassign n to Tide; wsm

"Associated 0110mm, San-Francisco, cans, a corporation-of Delawu-e ff Application May 9 ,1938, son mam-, S11 i (01. 190-35) 1 This invent on-creates to, "thehdistlllatlon or petroleum and the treatment of the same with alkalies such-as caustic sodarand has for its principal purpose the recovery of various oil fractions of suitable purity for commercial use.

A second purpose is the continuous 'dis'tillatlon of lubricating oiLfractionswith only a small fraction rejected as bottoms. yAthirdpurpose is the continuous distillation of lubricating oil fractions in the'presence ofvalkali A fourth purpose is to provides method for the continuousdistlllation of' lubricating stocks. inthe presence of alkali whereby the service factor-of thez'still is increased and the repair cost reduced; i I

other purposes will be apparent from the fol-. lowing description. 1 1

In the :distillationof lubricatingoils it is' common' practice to conduct the i distillation in the presence of caustic I soda or other alkali ,whereby acidic bodies; such as naphthenic acids and phe-V V "nols, are retained in thebottoms as soaps or salts of the alkali used; In continuous distillation the .alkaliis normally injected into the 'oil stream to "be distilledfi-The presence of this has a f corrosive action on theheating tubes andVOther ghighlyheated parts of the apparatus. Deposits of solider semi-solid alkali also form in the heat- I ing tubes-resulting in decreased heattransfer, v overheated tubes, decreased time on stream and increased repaircosts It-is therefore a purpose of this invention to provides. means for. removing 1 the major portion of the alkali from the oil before the oil enters the tube still.

l0 whereby the .various fractions are .lw-ecovereid free 1 of contaminants; 7

.been made toirfecycle these bottoms, or aportion :th'ereof, with ,the fresh charge to; reduce the amount of oil rejected. Such practice almost invariably results inincreased corrosion dueto the entrainedfalkali and in poorer'quality products due togthe asphalticmatterin th'e'bottoms. I

I It has been found that acidic bodies which are formed by the hydrolysis of'th'e soaps or by decomposition of a small portion of the oil in the heating tubes may be accumulated ina heavy traction on one of ithelower plates of the frac tionatingzone of the 'towerfwhich' fractibnmay "then be tul 'ned*tofthe"*still together with' 't'he flfreshicharge'iAny alkali entrained by the'vapors vis also -accumulated"in-this heavy fractiomand is 'thereby removed from theflnishedfdistillates. V The single sheet of drawings illustrates 'in l 'l'g. 9 LapreIerred for'm of fractionatlng column'in vertical section which is diagrammatically con- 20.

'of' 'utilizlngjthe invention and Figf2 shows a nected with 'otherfapparatus to show oneform inlxeror agitator for the chemical treatment of the oil withdrawn'from pipe 29.

' Lubricating 11 Jew-c1; to e amine-diam an- .taining only a small percentage "of asphaltic matter" (such as, forexample, once distilled lubricat-' ,mgnistmste; lubricating distillate from crudeoils low in, asphaltfor distillates which have been "previously treated by physical or chemical means) is forcedfrom llnel by'pump" 2 through heating coil 3, whichmay be: advantageously :a heat exchanger, where itis heated to a temperature suit- 'able'for alkali treatment. A temperature from .In' modernvacuum fractionatlng towers, par- 'ticularly. when steam is injected for stripping -purpos'es, there is a tendency for the soaps formed l to hydrolize. liberating free acidicbodiesuwhich are carried upv with the vapors to the lower plates v-"of the tower sometimes along with a portions of the alkali. -1To obvlate this contaminationit has 1- generally been necessary .to either inject large excessesofalkali to reduce thehydrolization' or to maintain a high rate oflrefluxing on the lower The injection of large The of the tower results in a large amount of valuable .heavy lubricating stock being-rejected swith tho a v v p v y bottoms" from the distillation. Attempts have so 9hamberthejso1utionoi soaps and "are more desirable'. Forlithis reason thefalkali 7 metalihydroxid'es and carbonateszare especiallyv preferredbut generally the hydroxides .and'car about 200 to'500' F. a v such treatment." To the oil leaving c011! through V 'pipe'l there is supplieda water solution or sushas been found suitable for pension-of alkalifrom pipela. Such alkali may be NaOH, KOH,Ca(OI-I) z, MgOH CaO; orany alkali found'suitable for combining witlrthe acidic compounds of them], although those. alkalis forming the most stable and'oil insoluble soaps bonates of both the alkali metals and alkaline earth metals can beused. Sufllcient alkali isused to combine with theacidic compounds. present in 1 the oil and the amount variesfrom a very small quantity, such as 0.01 pound, up to's5 pounds per barrel of oil, depending on the characterv of the oil tobe-treated..

From pipe '4 the oil and alkali pass into settling chamber-II; maintained under suiilcient pressure to hold the water in liquid form; From the setother gas, if desired, enters at lubricating fraction is lost as I this invention, however, the lowest plate 7 downpipe and the alkali is drawn off through valve 6 and pipe 1. Settling chamber may be of any design suitable for separation of the alkali solution from the oil under the pressure developed by the treating temperature. It may contain Raschigrings, bafiies, or the liketo assist in the settling of the alkali sludge. Mechanical separators such as centrifuges or filters maybe used, if desired, to facilitate the settling of the sludge. If, however, it is desired to further heat or distill the water may beoil with the alkali present, the flashed off from chamber 5 through valve 8.

When the oil carefully treated with sulphuric acid or solvent extraction, the alkali requirement generally does not exceed 0.2 its equivalent of other alkali) 'per barrel of oil. In such a case it may be well to distill the oil in the presence of this small amount of alkali in order to neutralize acidic materials which may be formed by decomposition of the oil during the subsequent heating.

The oil after treatment with the alkali passes from the settling chamber 5, through pipe 9, to the main heating coil l0, situated in furnace II and heated by burner i2, where it is heated to the desired temperature for distillation, suitable temperatures being well known to those familiar with the art of lubricating oil distillation. 7

From the heating coil the heated oil passes through transfer line It and control. valve lid to tower l4, which is preferably maintained under a to be distilled has been previously to 0.3 pound of caustic soda (or oriother suitable means not shown. Steam, or 0 through pipe l5 and distributing ring inthe vaporization and fractionatower l4 l6, and assists tionof the oil according to wellknown methods. Vacuum tower It contains a plurality of bubble plates or baiiles ll of conventional design through which the vapor and steampass and on which a .level of reflux oil is maintained to wash the va- A similar set of bubble plates'or baiiles I8 is preferably'placed below. the inlet of pipe i3 and above the steam inlet It to act as a stripping section. The steam inlet It may be replaced or supplemented by a heating coil or other source of additional heat if desired. 7, V I

On one side of each of the bubble plates H are situated weir boxes l9 so constructed as to maintain a desired level or liquid on each plate. The excess oil on each plate enters the weir boxes and is returned to the opposite side of the next lower plate through pipes 20 and valves 2| which are preferably controlled from ther outside of the tower. Excess oil not required to wet the next lower plate may be withdrawn through pipes}! by means of suitable pumps or suction apparatus 23.

The oil layer on the tionating zoneserves tion of the tree acids formed by the hydrolysis of the soaps. In conventional practice this oil is returned to the stripping section of the tower and passes out with the bottoms from the distillation through pipe 24 and thus a valuable bottoms. According to of the fractioning zone has no oil containing the impurities is'withdrawn from the weir box IQ of this plate through pipe .In this manner the amount 7 drawn from settling chamber The withdrawn oil is then cyclically returned to the process through valve 21 and pipe 28 and is mixed with fresh oil entering through pipe ii. of bottoms formed in and removed through pipe 24, is as 0.2%

the distillation, reduced to a very small percentage, such to 3.0%, and generally below 5% to 10%, of the oil distilled. The remaining oil is recovered as valuable distillate from the other plates of the tower.

The acidic'bodies cencentrated in the recycle oil from the lowest plate of the fractionating section are removed by'the alkali treatment along with the acidic bodies from the fresh oil charge. However, at times, and especially when soaps are not withdrawn from settling chamber 5 through pipe 1, there is built up in the system a gradually increasing amount of acidic compounds. In such cases a portion of pipe 25 can be removed from the system through valved line 2!. This removed oil may be discarded or used for lubricating equipment where the'presence of acidic bodies is unimportant or even advantageous. However, it has been found advantageous to chemically treat this withdrawn oil and return it to the system through valved line 30. r

Regardless of whether or not soaps are with- 5 (through pipe 1), decomposition products resulting from the heating in coil Ill accumulate in the oil' and it has been found desirable to close valve 21 and withdraw the entire' stream from the bottom plate of the fractionating section through line 2 9. This withdrawn oil is then treated with alkali, or preferably with acid, or with acid and then with alkali, and returned through line 30. Other treat-, ments, for example withclay, may be used instead of, or to supplement, the acid or alkali treatment to remove the acidic andzdecomposition products. To enhance the treating ofthis so withdrawn oil, which is highly viscous, and to avoid excessive emulsiflcation during its treatmerit it has been found advantageous to decrease may when a raw distillate is mixed with the viscous recycle oil, it is. obviously necessary to treat the mixture by whatever chemical treatment. that is required by the raw, light 'oil.

The described chemical or may be carried on in accordance with any well known or conventional process or apparatus 28. tained from various such as diagrammatically shown in Fig. 2, either ir'r batch or continuous treatments, but such speciiic treatments form no part of the present invention and can be generally illustrated as providing that the stream of contaminated oil drawn through pipe 28 may be passed, inwhole or in part,fin to any well known agitator or mixing chamber 3|. mainder. may be withdrawn through-pipe 12.

Acid may be introduced into the oil in agitator 3i through pipe for the desired period, the acid sludge can besettled and removed through pipe 34 and the purifled oil returned through pipe 30. In similar manner alkali or clay can be introduced through pipe 35 for the described purposes.

When operating in the above described manner it has been found that the oil fractions obfractionating plates, except the recycle oil passing through clay treatments 1 If only'a' part is treated, the re-- 33 and, after treatment therein 28 or by $66,359 the lowest, are of satisiactory qualityfor. commercial use and ordinarily-requireinojfurther treatment,- while the length. of time in which the still maynormally' operate without mechanical failure hasybeen increased over six' foldi Fol-- lowing 'are examples of color land coloristabilityf 'of various fractions obtained when operating the process on naphthenic baselubricating. stock which hasgbeen previously distilled and .acid

The invention comprises in lts fi t gb ing modes of operation:

. fractionally distilling the contacted oil to] retreated:i-

I. '3 hi 7 v Colord" Viscosity oHractionS.:U.stlw r. Lovibond Q23 5??? Lovibondcell .nal charge; g I '3. The method '(l)' When an oil either containsacidici compounds, such as-naphthenic .acids, or'has beenso treated with acids, such as sulphuric acid, or ,with= liquidYSOz' that: it contains residual acidity, then "suflicient alkaline solution is added'throughpipe 7 la tojneutralize such 'acidi'c compounds. andito 1 "remove the neutralization products -.in settling chamber 5.

" (2) Whnan oil contains no acidiccornpounds x as above stated, there is, however, ,agdecided "tendency for acidic'compounds tobe formed in heating-coil -l 0 together with decomposition product's'ln' whichan alkaline solution in relatively small amounts will beintroduced through pipe, ltfsuiilcient to neutralize such .iormed acidicv ,LcomP unds.

I 'This small amount'of-- alkali need not ejrceed uid phase through pipe I: leaving onlya minimum quantityof-anhydrous alkalito pass through coil i0 and in this event formed acidic compounds V willeither be removed by recycling through-Pipe chemical' treatment prior to such recycling.

Alternatively, when required, when ;-water'is flashedoii' through valve'i, therewill generally v be no liquid withdrawal-through pipe-l; and a relatively large amount of anhydrous alkali passed through coil ll which will further neu- "tralize any acidic compounds formed in coil lll.- The temperature towhichtheoil is heated in contacting v'hydrocarboni oil containing acidic mov n ss';than-about 97% as distillatesi'and recovering from: said distillation a relatively low boiling fraction substantially free from acidic bodies, an intermediate fraction containing acidic bodies; and a bottoms fraction between "about,0.2 and 3.0% of 'the'origlnal charge. ,Thefmethod' of treating? oil which 'comprises, contactingjhydrocarbon' oil containing' acidic'compoundsfwithan alkali-in the presence of water at a: temperature between- 200. and

'*500'1?., under pressure sufllci'ent' to' prevent :sub:

staritialvjaporization oi the water, separating-the resulting agueouslayer, fractionally distilling the contactedoil to remove not'less than about 97% 'as di'stillateaiand recovering --from said distillation a relatively'low boiling fractionsubstantially free "from acidic -bodies, an intermediate fraction containing acidic bodies; andza bottoms fraction between about '0.'2% and-f3;0% of theorigiof treating-oil which compass,

compounds with an alkalfin the presence-of water ata temperature between 200? and. 500F.,

flashingfofl the water'irom "the mixture 'of 'oil and alkali; fractionally distillingthe: contacted oil to removenot less than about 97% *as. dis- .t'illa't'es; 1 and recovering from said'distillation a relatively lowboilingjfraction substantially free from acidic bodies,an interrnediate fraction containing acidic bodies, and a bottoms fraction between about 0 .2% and 3.0%}01 the original char'g eikjlsf v, v g ,The'method of treating oilwhichcomprises]contacting a;hydrocarbon ,oll low inf-asphalti cr content and "containing acidlc compounds with fan alkali metal-hydroxide in L the presence "of water at atemperature between 200 and 500 F., fra'ctionally distilling the contacted.

oil; torem'ove not less than about*97% as disi 'tillates,j andrecovering from :said' distillation a relatively low boiling fraction substantially 1 free from acidic bodies, an intermediate fractionicontaming acidic bodies, and a bottomsfraction between "about charge, v r v V a 5. ;Thef method of treating oil -which comprises; contacting a lubricating hydrocarbon oil low; in fasphaltic content and containing acidic compounds with'jan alkali in thepresenceof-wa- 0.2% and 3.10% r of the original -terat a temperature between mound 500. F., fractionally distilling J the contacted oilunder vvacuum to remove not-lesswthan about 97% as distillates, recovering froiifsaid distillation a reiatively lowboiling fraction substantially'ir'ee from acidic bodies, an interm'ediate fraction containacidic.bodies,"and a bottom fractionlbetweenabqut- 0.2%, n s-0 Q h coil i0 is generally sufficient for distillation purposes only and, for vacuum distillation of lubri eating oils, is not such as would cause substantial decomposition or cracking, but any decomposition is incidental and unavoidable.

At the same time. while describing the invention in a preferred form. it is intended only to be limited in its application as set forth in the appended claims.

We claim as our invention:

1. The method of treating oil which comprises,

. contacting hydrocarbon oil containing acidic compounds with an alkali in the presenceof wa-' ter at a temperature between 200' and 500" R,

6. Themethod of treating oil which comprises, contacting a lubricating "hydrocarbon on low in asphaltic content and containing acidic compounds with an alkali in thepresence of water' at a temperature between 200 and 50091 2, fractionallyfdistilling the contacted .oil under vacuum to remove not less than about 97% as distillates, recovering from said distillation a relatively low boiling fraction substantially free from acidic bodies; an intermediate fraction containing acidic bodies, and a bottoms fraction between V about 0.2% and 3.07% 01 the original charge, and

I recycling at least a portion of said intermediate fraction to the alkali contacting step. r

7'. The method of treating oil which comacidic and decomposition step. 1

- phuric acid, and returning such contacting lubricating hydrocarbon oil con ing acidic compounds with an alkali in the presby blending prises, contacting hydrocarbon oil acidic compounds with an alkali in the presence 'acidic, bodies, and a. bottoms traction between the original charge,.

about 0.2% and 3.0% treating said intermediate fraction to remove bodies, and returning such treated fraction to thealkali contacting 8. The method of treating oil which comprises, contacting hydrocarbon oil containing acidiccompounds with an alkali in the presence of water at a temperature between 200 and 500 F., fractionally distilling the contacted oil, re covering from said distillation a relatively low boiling fraction substantially free from 'acdic bodies, an intermediate fraction containing acidic bodies, and a bottoms traction between about 0.2% and 3.0% of the original charge, treating said intermediate fraction with sultreated fraction with the fresh charge to the alkali contacting step.

9. The method of treating oil which comprises,

tainence of water-at a temperature between 200 and 500 F., fractionally dist'llingthe contacted oil, recovering from said distillation a relatively low boiling fraction substantially free vfrom acidic bodies, an intermediate fraction containing acidic bodies, and a bottoms iractionbetween about 0.2% and 3.0% of the original charge, reducing the viscosity of said intermediate fraction therewith a low bon oil, treating the resulting blend with sulphuric acid, and introducing the treated blend with the fresh charge to thealkali contacting step a j 10. A process of treating oil which comprises, flowing a continuous stream or hydrocarbon oil containing acidic compounds and alkali through a heating stage under superatmospheric pressure, expanding the mixture into a fractionating zone of lower pressure wherein the majorv portion of said oil is vaporized, iractionally condensing said vaporized oil in said zone, and separately withdrawing uncontaminated condensed iractions and contaminated condensed fractions to leave a bottoms fraction between 0.2% and 3% of the original charge.

11. A process of treating oil which comprises,

i the oil containing viscosity hydroc-aring uncontaminated I panding the mixture into a fractionating zone of lower'pressure wherein the major 'oil is vaporized, iractionally condensing said vaporized oil in said zone, and separately withdrawcondensed fractions and contaminated condensed fractions to leave a bottoms fraction between 0.2% and 3% of the original charge. a

12. 'In a process f refining lubricating oil containing acidic compounds in which the oil is heated in the presence of an alkaline material and then fractionated to obtain a series of distillates I varying in gravity, the combination of steps which'comprises, withdrawing the heaviest distillate of said series from the iractionating step, treating said-distillate to remove acidic and decomposition products resulting from said heating, and returning at least a portion of such treated distillate to said heating step.

13. In a process of refining lubricating oil containing acidic compounds in which the oil is heated in the presence of an alkaline material and thenfractionated toobtain a series, of distillates varying in gravity, the combination of steps which comprises, withdrawingv the heaviest distillate of said series from the iractionating step, mixing a lower viscosity oil with said distillate, treating the mixture to remove acidic and decomposition products resulting from said heating, and returning at least a portion of such treated distillate to said heating step.

14. Aprocess of refining oil which comprises: mixing hydrocarbon oil heated from about 200 to 500 F. with an aqueous alkaline solution, re-

moving the water of solution, further heating substantially anhydrous alkali to a temperature'at which not less than of the oil will vaporize at, a reduced pressure, expanding the heated oil to cause such vaporization, withdrawing the unvaporized oil, iractionating the thusvaporized oil, withdrawing the heaviest fraction thus obtained, and returning the said heaviest fraction to the said mixing step.

15. A process of refining oil whichcor'nprises: mixing hydrocarbon oil heated from about 200" to-500 F. with an aqueous alkaline solution,'removing the water of solution, further heating the oil containing substantially anhydrous alkali to a 'temperature at which not less than 90% of the oil will vaporize at areduced pressure expanding the heated oil-to cause such vaporizaflowing a continuous stream of hydrocarbon oil 7 containing acidic compounds and an aqueous alkaline solution through a heating stage under suoeratmospheric pressure, separating. at least a portion of said solution from said mixture, ex-

- THOMAS OLIVER EDWARDS, JR. OSCAR LARSON.

portion of said I

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