US2733187A

US2733187A - Liquid-liquid treating process

Info

Publication number: US2733187A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 w. M. BASCH 2,733,187

I IQUID-LIQUID TREATING PROCESS Filed March 19, 1952 DISTILLATIOH 'Zoura.

TREATING;

Zone 1 Mai hi2. @asc B o'Jm/enbor' Clboorrzeg United States Pate 2,733,187 "LIQUID-LIQUID TREATING'PROCESS Application March 19, 1952, Serial No. '27 7 ,508

.1 Claim. .(Cl..196.14.42)

The present invention is concerned with an improved process for the production -of high quality lubricating oils. The invention is -more particularly directed toward an improved liquid-liquid contacting process wherein .solvents having a preferential "selectivity for'the more aromatic type constituents are utilized for the treatment of oil fractions. In accordance with the present invention, solvents of this character, as for example, phenol, are .efliciently recovered by utilizing a partial crystallization operation in conjunction with a distillation operation.

It is well known in the art to contact hydrocarbon fractions with solvents having a preferential .selectivity for the more aromatic type of hydrocarbon constituents as compared to the more paraffinic type hydrocarbon constituents. Solvents of this character are for example, phenols, .furfural, .sulfur dioxide, ..nitrobenzene, aniline, cresols, chlorex, dimethylformamide, dipropionitriles, ammonia, amines, etc. It is also known in the art to use in conjunction with these aromatic type solvents, solvent-modifying agents as for example, water, alcohols, esters and the like. Temperatures usually employed in the treating operations are in the range from about 40 F. to 250 F., while the solvent to oil ratios are in the range from about 0.4 to volumes of solvent per volume of oil. These operations have been carried out either in batch or in countercurrent treating zone processes.

While the solvent treating operations, as described and known in the art, have been entirely satisfactory for segregating the desired fractions and for improving the viscosity index and other critical factors of oils such as lubricating oil and the like by the removal of aromatic type constituents, certain difiiculties have been encountered. For instance, it has been relatively difficult and expensive to separate the solvent from the rafilnate phase and from the solvent extract phase. While distillation is a conventional procedure, other methods have been suggested. Cooling of the respective phases has been utilized to separate a solvent-rich phase which is returned to the treating zone. This is not particularly desirable since not only does the solvent-rich phase contain a considerable amount of oil but also this retained oil is of a relatively high aromaticity content which is not suitable for returning to the treating zone.

In accordance with the present invention, the phases, particularly the solvent extract phase, is cooled to crystallize the solvent such as phenol. The crystallized phenol is separated from the liquid phase, preferably under pressure. A very desirable mode of operation is to filter the crystallized phenol or equivalent solvent from the oil, then to press the crystals to remove oil therefrom followed by reheating and recycling of the phenol to the treating zone. Phenol separated by distillation is returned to the treating zone at a point above the point of introduction of the phenol segregated by crystallization.

The process of the present invention may be readily understood by reference to the attached drawing illustrating embodiments of the same. Referring specifically to the figure,

a lubricating oil fraction is introduced into the bottom of countercurrent treating zone 1 'by means of line 2. An aromatic type solvent, preferably a phenol, is introduced into 'the'top of 'countercurrentitreating zone 1 by means of line 40. In accordance with .the procedure of the present invention, phenol secured as hereinafter described "is introduced into treating zone 1 .at a point below the point of introduction of the pure vphenolsby means of'line 3. The quantity of phenol used 'i'o1,;1mrposes of illustration is in :the range from about 0.4 .to 3 volumes of phenol per volume of oil. Temperature conditions in the countercurrent treating tower are in the range from about 1'1'0 F. to 250 F. 'It is preferred that the top temperature be in the range "from about 130 F. to 250 F., while the temperature at theb'ottom of the tower be in the 'range from about 110 -F.' to 210F. A raffinate phase comprising phenol and parafi'inic'type constituents is removed overhead from zone 1 *bymean's of line 4 and passedtoadistillationzone 5. Temperature and pressure conditions in distillation zone 5 area'dapted to remove overhead by .means iof line 6 phenol which is preferably recycled to line 40. A high quality lubricating oil product is removed from the bottom of .distillation zone 5 by means of line 8.

A solvent extractphase is removed from the bottom of extraction zone 1 by means of line 9 and passed to :a

chilling zone 10. Temperattute and pressure conditions in zone-10 are adapted to precipitate thephenol. The phenol is removed from chilling zone 10 by means of line 41 and introduced into a filtering zone 42. In-zone '42 the precipitated crystals are separated from the liquid phase whichis removed from zone 42 by means of line 43. This liquidphasefis introduced into a distillation zone 13.

Temperature and pressure conditions in zone :13 are adapted to remove overhead by means 70f line '14 the phenol which is preferably recycled to the system by means of line 40. A solvent-free extract oil is removed by means of line 15 and handled or further refined as desired. It is to be understood that

zones

1, 5, 10, 42 and 13 may comprise any suitable number and arrangement of stages.

The solvent crystals removed from zone 42 by means i of line 44 are preferably passed to a pressing zone 45. In this zone the crystals are pressed to remove oil which is passed to distillation zone 13 by means of

lines

46 and 43. The solvent crystals are removed from zone 45 by means of line 47, heated in zone 48 and recycled to zone 1 by means of line 3.

The present invention is broadly concerned with an improved solvent treating operation wherein the solvent is efficiently recovered from the segregated phases. The method broadly comprises cooling the phase to precipitate the solvent which is separated from the liquid phase by filters, centrifuges or the like. It is preferred that the segregated crystals be then subjected to pressure in order to remove remaining traces of the oil. The pressed crystals are reheated and recycled to the system at a point below the point of introduction of the solvent which has been segregated by distillation.

The invention is particularly applicable in the handling of a phenol solvent wherein the water content of the solvent is maintained below about 4%, preferably less than about 2% by volume based upon the phenol. It is preferred that the solvent extract phase be chilled to a temperature below about 100 F., preferably to a temperature in the range from about 65 to F. It is also preferred that the crystals be subjected to a pressure in excess of 50 to lbs. per square inch. Operating conditions should be adjusted to secure a solvent extract phase having an oil content less than about 8%, preferably having an oil content less than about 5%. Under these conditions, by the procedure of the present invention 40 to 60% of the solvent is recovered by the procedure out- 3 lined, thus reducing the load on distillation equipment by about 50%. The process of the present invention may be more fully understood by the following example illustrating the same.

was solvent extracted. The temperature employed at the top of the zone was 140 F., while the bottom temperature was 130 F. About 1.4 volumes of phenol per volume of oil was used. In one operation the phenol had a water content of 7%, while in the second operation the water content of the phenol was 0.5%. The data on the solvent extract phase from the respective operations were as follows:

Recovery of crystallized phenol from phenolic extract llsmg press Phenol in Extract, Vol. Percent G9 65 B in Phenol, Vol. Percent 7 0. Pressing Temperature, F 55 81 Results alter Pressing:

Phenol Content of Filtrate 47 Phenol Melting Point, F 101 104 Phenol Oll Content, Vol. Percent. 1O 4 Percent Recovery of Phenol G6 83 From the above it is apparent that the phenol secured from operation B was very satisfactory in that it contained only 4% by volume of oil.

What is claimed is:

Improved process for segregation of more aromatic type constituents from more parafiinic type constituents of a petroleum oil, which comprises introducing said petroleum oil into the bottom of a countercurrent treating zone, introducing substantially pure phenol into the top of said countercurrent treating zone, maintaining conditions in said zone to secure a raflinate phase and a solvent extract phase having an oil content of less than about 8%, separating said solvent extract phase and chilling the same to a temperature below the crystallization temperature of phenol to crystallize a substantial proportion of the phenol content thereof, removing phenol crystalsfrom said solvent extract phase, subjecting the same to pressure in excess of about pounds per square inch and removing oil therefrom, reheating said pressed crystals and recycling said phenol to said treating zone at a point below the point of introduction of said substantially pure phenol, and subjecting said solvent extract phase from which said crystals have been removed to a distillation zone wherein substantially pure phenol is separated from said extract and recycled to the top of said treating zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,779,287 Pfafi et al. Oct. 21, 1930 1,820,645 Bennett Aug. 25, 1931 2,216,933 Atkins Oct. 8, 1940 2,557,406 Blazer et al. June 19, 1951 OTHER REFERENCES Norris: Experimental Organic Chem., 2nd Ed. (1924), pages 7 and 8, McGraw-Hill, 330 W. 42nd Street, New York, N. Y.