US2324952A - Refining of mineral oils - Google Patents

Description

July 20, 1943. Q READ 2,324,952

REFINING OF MINERAL OILS Filed Feb. 10. 1940 .3 4 VENT .SEPA RA 7- COOLER .5534 RA'TOR L RA FF/NA r:

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' spective constituents is secured by suitable dis- Patented July 20, 1943 UNITE D STATES f PATENT asrmmo or MINERAL OILS i.

Chester L. Read, W'estfield, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application February 10, 1940, Serial No. 318,249

2 Claims. (01. 196-13) The present invention relates to the refining of mineral oils. The inventionis more particularly concerned with the segregation of petroleum oils into their relatively more paraiiinic and into theirrelatively more. aromatic constituents by means of selective solvents. In accordance with the process of the present invention, distinct improvements are secured in solvent treating operations by pretreating the feed oil in the presence of arelatively small amount of the selective solvent in a manner adapted to remove relatively minute quantities of substances which are entirely insoluble in the selective solvent under the conditions of operation and which would otherwise result inoperating difficulties. V

It is well known in the art torefine mineraloils and to segregate these oils into their relatively more aromatic and into their relatively more paraffinic constituents by means of various selective solvents. In processes of this character the general procedure is. to-extract the mineral oil with solvents of the class which have a preferential selectivity for the relatively more aromatic type compounds as compared to the relatively more paraffinic type compounds. Sol- Vents of this character are, for example, furfural, phenol, sulfur dioxide, cresol, nitro benzene, aniline, beta beta dichlor diethyl ether, and the like;

7 The oil and solvent or solvent mixture are mixed in various types of operations undertemperatureand pressure conditions adapted to form a highly aromatic or solvent extract phase and ahighly paraflinic or raflinate' phase. Although single or multi-stage treatments are employed, the preferred process is a countercurrent tower treating operation, since it is continuous and permits a more economical operation. In a countercurrent tower treating process the lighter phase, usually the oil, is introduced at the bottom or at the center section of the tower. This phase flows upwardly through the tower and intimately contacts the downflowing heavier phase, usually the solvent, which is introduced at or near the Complete mixing of the re tributing and contacting means, such as distributing plates, pierced plates, contact masses, and the like. If the oil is the heavier phase, the conditions are reversed and the oil is introduced at the top of the tower, while the solvent is introduced at a lower section of the tower. In a countercurrent treating tower operation either the oil or the solvent may be the continuous phase, although it is generally preferred that the solvent be maintained as the continuous phase. The efficiency of a 'countercurrent treating tower operation is a function to a large extent of the e'fiiciency of the contact betwe'en the respective phases, as well as upon thetime of contact. However, when usingcertain solvents, particu larly phenols, it has been found that-certain oils contain constituents which cause extended emulsification, of the, solvent and oil. This greatly lowers the overall efiiciency of the sol vent treating'operation, since the emulsification zones in effect decrease the efiective area of the tower, resulting in a. decrease in capacity. and yields. My process, which comprises a pretreatment of theoil in the presence of 'a relatively small amount of the Iselective'solvent, entirely eliminates emulsification and related operating, dimculties and .resultslin' unexpected improvement in tower capacities and in products of improved quality. V,- fl

The process of my invention may bereadily understoodby reference to theattached drawing illustrating one modification ofthe same. Feed oil, which for the purposes of description is taken to be astock substantially free of asphalts and resins and boiling in the-petroleum lubricating oil range is introduced into the solvent treating system by means of line l ,The feed oil-is mixed with a relatively small amount of solvent, which for the purposes of illustration is assumed :to be a phenol, which is introduced into line I by means of line 2. The mixture'is passed through ature, and introduced into main solventtreating unit 8, which for thepurposes of description is assumed to be a countercurrent treating tower. The feed oil flows upwardly through tower 8 and countercurrently contacts substan tially the entire quantity of phenol which is introduced into countercurrent treating. tower 8 by I means of line 9. Efficient con-tact between the .countercurrently flowing phases is secured by adequate contacting means such as distributing plates, contacting masses, pierced plates, and

the like. The selectivity and solvent power of the selective solvent may be adjusted to any desired degree by the instroduction of a solvent modifying agent such as water into tower 8 by means of lines In, H, l2, and I3. Temperature and pressure conditions are adapted to secure the formation of a highly paraflinic or rafllnate phase which is withdrawn from tower 8 by means-airline M. .This phasemay be cooled in cooler .5 or mixed .with a solvent modifying agent which is introduced by means of line IS in order to secure a further phase separationiin separator IT. The precipitated solvent .rich phase is withdrawn from separator 'l'lby'means of line I8 and handled in any manner desirable. This phase may be returned to .theacountercurrent treating tower or utilized as an intermediate stream. Under certain conditions it maybe desirable to use this phase relatively rich in 501- vent to dilute the feed oil prior to pretreating'the same. The .relatively solvent poor phaseis withdrawn 1mm -separator n by means .of "line :19 and passed'to "solventiseparatorflln which the solvent is "removed by -.means offline 21 and :returned 10 solvent storage 12. A solvent-tree 'ramnate oil "is withdrawn by means of line T23 and removed from the system.

"The solvent extract :phase may be similarly handled. This phase is "withdrawn Tfrom tower 18 by :means of '24 and 'may be cooled 'in eoiolerzi in order "to secure a. Turtlrer phase sep- 'aration in separator 26. fPhase senaratton may be aided or entirely secured .by 'theaddition of a solvent modifying agent which is fintroduced byxrreans of line -fl. The preclpitatedphase'is withdrawn 'tromseparatorlfi by means of fline -28. "and handled in any manner desirable. "This phase may be returned ito the 'countercurrent -treating system .or removed -an intermediate product. The solvent "rich phase .is withdrawn from separator Zliby means of linen'and passed to solvent "recoveryunit 301mm which the solvent is removed "by means of line 3| and ireturnedtosdlvertt storage 22. A' solvent-treeiex- 'tractiiswvithdrawn tromunltmby means of line 32, removed from the system, :and .handled in anymanner desirable. Under pertain conditions 'be'desirahle to utilize a small amount of relatively solvent rich phase withdrawn spective phases. These di'lhculties are generally measuredin terms or 'emulsrftcation. In general, I have found that these constituents comprise -lessthan about 2% more feed oil and are gen- 'erally'in the *range from i01% to 115% of the reed'oil.

lhe amount of solvent introduced in the chargeo'il before pretreathig the same .rn ay vary widely. The quantity-will upon the particular solvent beingused *andthe character of the *ieed'oilbeingsolventtreatedgaswell as upon the temperature or the oil. it is "flesired to introduce sufficient solvent into the charge oil to approximately saturate the oil with solvent which results in the precipitation of substantially all of the solvent insoluble oil constit- 5 uents without the formation of two phases containing an appreciable amount of the selective solvent. For example, when using henol, I have found that it is desirable to dilute the oil with from about "6% to 20% 0f phenol, ;preferably 10 from 10% to 112% of .phenol before .pretreating the same. This results in the precipitation of .about 0.01% to 0.5% of solvent insoluble constituents. The temperature of the pretreatment *maylikewise vary considerably, In general, the rtemperature is preferably in the range below about '150-F.-depending upon the particular solvent employed. The pretreated oil after removal of the solvent insoluble constituents is then heated or cooledto optimum tower countercur- ,go rent {treating temperatures. When employing phenol as the selective solvent in the treatment 'of petroleum oils boiling in the lubricating oil range, I have found that it is particularly destrable to approximately saturate the oil with phenol at a *temperature in the range below about 1 10 B. to 125 F. under conditions to;pre cipitate'arela'tively'small percent of scilventinsolubleoil constituents withoutthe formation'of two phasesconta'in ing an --appreciable amount of 'the selectivesolvent. *Feedoil isthen'filtered-to remove the insoluble constituents-and then heated to optimum countercurrent treating temperatures generally in the range from about 150 F. to 225 F.

In order to 1 further illustrate the invention, the following example is given which should not be construed as limiting the invention-in-any mannor whatsoever:

. Example A lubricating oilhaving a "viscosity-of 135 Baybolt at210 -F., a-gravity of 2434 A. 'P.-I.-derived drom Rodessa crude and'which had been previpuslyacid treated and s'teamsweetened to remove the asphaltic constituents was solvent treated with phenol in various operations. In the first :operation the "feed oil was passed directly into a --eounterourrent treating tower. In asecond-opcreation the feed 'oil was filtered usingcentrifuges I and then 'passed irito :the counter-current treating tcrwer. In a l third operation a propane 'pre cipitatod oil :was passed directly into a countercurrent treating tower. "-In a fourth operation conducted -in accordanee -with the process =dfthe present invention the "feedoil-wes saturated with phenol, filterediby'means of press filters 'and'then passed into the countercurrent treating "tower.

'l 'heresults of these operations wereas' follows:

00 Per cent phenol Maximum Percent cainsolu le..oil tower capacity; Dacity based meterialin all volumes of oil upon-operadeed iced per hour tioml Operation 1 0.124 400; -13. 3 Operation'.2 c '0. 13 620' 20. 7 Operation 8, 0.03 2,30] '76. 6 QperahionA 0.01 3, 000 JLOO. 0

it is desired to claim all novelty in so far as the prior art permits.

I claim:

1; In a process for segregating into its relatively more aromatic and into its relatively more parafiinic constituents a viscous petroleum lubricating oil substantially free of asphalts, which tends to develop emulsification difliculties during solvent extraction, due to the presence in said oil of a small amount, less than 2%, of dissolved material which precipitates out during solvent extraction in the form of a finely divided insoluble solid which distributes itself between the interfaces of the solvent and oil, the improvement comprising subjecting said oil to preliminary treatment at a temperature between about 110 F. and 150 F. with a solventhaving a preferential selectivity for the relatively more aromatic compounds as compared tothe relatively more,

tion with a large enough volume of the same selective solvent and under suitable temperature conditions to cause the formation of two liquid phases.

2. In a process for the segregation into its relatively more aromatic and into its relatively more parafiinic constituents a viscous petroleum lubricating oil having a viscosity of about 135 seconds Saybolt at 210 F. and a gravity of about 24.4" A. P. 1., derived from a Rodessa crude oil, and which had been previously acid-treated to remove asphaltic constituents, which comprises mixing with said oil at a temperature of about to about F. a sufiicient amount of phenol, between about 5% and about 20% to approximately saturate said oil therewith but insufiicient to cause the formation of two liquid phases, to precipitate a small amount, less than 0.5% of the feed oil, of phenol-insoluble constituents as a filterable solid phase, filtering said oil in a press filter to remove said solid precipitate and to produce a filtered oil free from emulsifying tendencies when subjected to phenol extraction, and then countercurrently extracting said filtered oil with phenol at a temperature of about F. to 225 F.

CHESTER L. READ.

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