US2943992A

US2943992A - Separation of oil and wax

Info

Publication number: US2943992A
Application number: US565839A
Authority: US
Inventors: Harold S Blisard; Elmer H Smith; Richard K Rockstroh; Jack A Guthrie
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1956-02-16
Filing date: 1956-02-16
Publication date: 1960-07-05
Anticipated expiration: 1977-07-05

Description

y 1960 H. s. BLISARD ETAL 2,943,992

SEPARATION OF on. AND WAX Filed Feb. 16, 1956 Oil Wash

Solvent Reflmnq Reflmng Light Ilcarbons Vacuum Silll INVENTORS HAROLD S. BLISARD. ELMER H. SMITH RICHARD K. ROCKSTROH JACK A. GUTHRIE ATTORNEY Crude Oil Feed SEPARATION OF OIL AND WAX Harold s. Blisard, Springfield, Elmer H. Smith and Richard K. Rockstroh, Media, and Jack A. Guthrie, Springfield, Pa., assignors to Sun Oil Company, Philadelphia,

. Pa., a corporation of New Jersey Filed Feb. 16, 1956, Ser. No. 565,839

3 Claims. (Cl. 208-33) This invention relates to the separation of oil and wax, and particularly relates to a process for dewaxing petroleum mineral oils and deoiling petroleum waxes.

United States Patent No. 2,726,990 describes a process for the separation of oil and wax. According to the process, petroleum fractions of different boiling ranges are separately dissolved in solvents therefor and the solutions separately chilled to precipitate wax. The soformed slurries are then admixed and the wax separated from the admixture by filtration. Also, according to the process, the mixing of the two fractions at any point prior to the chilling operation should be avoided.

It has now been found that by admixing a relatively small, critical quantity of the lower boiling fraction with the higher boiling fraction prior to chilling, filtration rates for the separation of wax from oil are markedly improved and other advantages are obtained. It is essential, however, that the two fractions, after the addition of a small amount of the lower boiling fraction to the higher boiling fraction, be separately chilled and that the slurries resulting from the chilling be admixed prior to filtration.

In an embodiment of theprocess of the invention,-

topped crude oil is distilled to produce a distillate and a residual fraction. These fractions are advantageously refined to remove undesirable constituents, such as aromatics and asphalts. After refining, a small quantity of the distillate fraction is introduced into the residuum fraction. The quantity of the introduced fraction must be wtihin the range of from 5% to by volume based on the quantity of the residuum fraction. Solvent having a preferential solvent power for the oil is then advantageously added to both the distillate and residuum fractions to form solutions thereof, and the so-formed solutions separately chilled to a temperature sufiicient to precipitate a major proportion of the wax therein. The chilled slurries are admixed and wax is separated from the mixture by filtering.

By introducing a small quantity of the distillate fraction into the residuum fraction, it has been been found that the filtration rates for separating the precipitated wax from oil are improved so that, in effect, the capacity of the filter is substantially increased. This results in a large increase in the quantity of oil and wax which can be produced from the same equipment.

Attention is now directed to the accompanying flow diagram which illustrates a preferred embodiment of the present process. Crude oil feed is introduced through line '1 into vacuum still 2. The crude oil may be subjected to a prior distillation (not shown) for removal of light hydrocarbons, such as gasoline, naphtha and gas oil. Light hydrocarbons, or remaining light hydrocarbons, such as gas oil, are removed from still 2 through line 4. A distillate fraction boiling in the lubricating oil range is removed from still 2 through line 5, and a residual stream is removed from still 2 through line 6. It is usually desirable to subject each stream to a refining operation, preferably solvent extraction, to remove aro- "lee matics from the distillate stream, and aromatics and asphalt from the residual stream, as indicted by 8 and 9, respectively. After the refining step a small quantity of the distillate fraction is introduced through line 7 into the residual fraction. A solvent is then introduced through line 10 and admixed with the distillate fraction in line '11, the temperature at some stage of admixing being suficient to obtain dissolution of the distillate fraction in the solvent. Solvent is introduced through line 12 and admixed with the mixture of distillate and residual fractions in line 14, the temperature at some stage of admixing being suflicient to obtain dissolution of the mixture of fractions in the solvent. If necessary or desirable, a separate vessel may be provided to obtain complete dissolution of each fraction. The solution of the distillate fraction passes from line '11 to chiller 15 wherein wax crystals are precipitated to form a slurry. The solution of the residual fraction passes from line 14into chiller 16 wherein wax is precipitated to form a slurry. Theso-formed slurries pass from

chillers

15 and 16 through

lines

18 and 19, respectively, are admixed in line 20 and passed to filter 21. If desired, the small quantity of distillate can be introduced into the residual fraction after the introduction of solvent as, shown at 12, but it is essential that the addition be made prior to chilling as shown at 16. v

Filtration is advantageously accomplished by means of a rotary vacuum filter having provision for supplying wash liquid to the filtered wax and subsequent drying by suction. Separate continuous take-oils for the washed Wax cake, used wash, and filtrate are provided. Wash liquid is applied to the filtered wax cake through line 22; used wash passes out through line 24 and may be recycled preferably after stripping to remove dissolved oil and any wax that may be present. Filtrate is'removed through line 25 and passed to a distillation unit (not shown) in order to. separate the solvent, which is re as by filter pressing, and good results obtained there' with. Valves, pumps, heat exchangers, and the like, the location and operation of which will be apparent to those skilled in the art, have been omitted from the diagram. v

The dewaxcd oil after separation of solvent is subjected to distillation in order to form the desired fractions.

The solvent employed should have a preferential solvent power for the oil, should dissolve wax at relatively high temperatures, and precipitate wax at relatively low temperatures. A mixture of a wax anti solvent, such as methyl ethyl ketone, and an oil solvent, such as benzene, gives good results, and a mixture thereof containing approximately equal parts by volume is the preferred solvent, but either of these components may be replaced, in Whole or in part, by other materials. For example, other ketones such as methyl butyl ketone or acetone may be substituted for methyl ethyl ketone, and toluene may be substituted for all or a part of the benzene. It is preferred to employ the same solvent for dissolving each fraction from the initial distillation, since recovery of solvent after admixing the slurries and filteringis less difiicult than if diiierent solvents are employed. .The

wash liquid for the wax cake is also preferably the same as the solvent, and should be cooled to approximately the same temperature as the temperature of filtration be-' I F.', or fractions-n 3 present invention, two fractions, a distillate fraction and a residual fraction, are prepared by the initial distillation. The distillate fraction usually has a boiling range of from about 650 to 900 F. at atmospheric pressure. The residual fraction usuallyhas aboiling range of above 850.? E. at atmospheric pressure. Anpverlapping ofthe distillatenand residual. boilingrangehas no deleterious effects. Theprocess'. of the presentinvention may also be employed to-dewax, oil from two distillatefractions;

of diiferent'boiling' range. Suchdistillate fractions may the samedi stillation operation, but fractionsof difierent boiling ranges obtained. from. separate sources may be employed. Theg prpcess of the present invention may,

thus be employed to separate wax and oil contained in wax-oil mixtures having different boilingranges. V is accomplished as above described, byintroducing a 7 'small quantity of; the lower boiling wax-oil mixture into 'the higher boiling-wax-oil mixture, and separately treating each wax-oil mixture asufollows: dissolving the mixdissolutio'n, chilling the solution to produce wax crystals andform a slurry, combining the separately formed slurries: and filtering theicombined; slurries. ,In chilling.

the. solutions to produce wax crystals, atleast 10% of the Wax present in each fractionmust' be precipitated before combining' theslurries. The filtrate from this distillation to prepare a distillate fraction and a residual fraction. From to 20% by volume of the distillate fraction, based on the residual fraction, is added to the residual fraction. The fractions areseparately dissolved in a solventat a temperature sufiicient to obtain dissolution. The solvent is advantageously the same as above de,-'

scribed for deoiling wax. The solutions are separately chilled to precipitate ;wax to form wax slurries. The

' slurries are admixed and the combined slur-ties filtered.

This" ture in a solvent at a temperature sufiicient to obtain constituted' an;80%. yield of oil, theoil'content'of the, wax produ'ct was. 15%. In this operation, the distillateoperationmay;l e-separated intoithedesired oil products by distillation. In this :final'distillation, the oilproducts may be separated at the; same temperature. and pressure as the initial fractions. The process, however, is not so limited; any desired; oil fraction, or fractions may be *7 obtained Itis of advantage-in some instances to. employ a small quantityof' amaterialknown to. assistin a filtering opera tion. The material selected, however, should not dele-' teriouslyafi'ect the waxproduction, or should. be readily,

separable from; the wax. The quantity of such material should not be above-about 0.1% by volume of the oil' charged, and" isusuallywithinthe range of from 0.01 to 0.08% by volume. of the oil charged. Such added mate rial, when used; can be introduced priorto, or after the chillers in either or both ofthe low boiling or high boiling fraction. Such addition is especially advantageous indecreasing the quantity of oilseparated with a slack wax on thefilter; and in decreasingthe quantity of wash liquid required in the filtration operation. Materials that '7 fraction passing to its sparate chilling at 520 barrels per day. 'Itwas found that by. this operation, the" filtration The separated oil-free wax isdistilled to produce; thei desired products.

In this embodimentofithepresent process, the/same V advantages as described for dewaxing: oil areiob tained,

'fj namely, an enhanced rate of filtering wax from oil, a f' decrease in the quantity of solvent and wash liquid re; quired with a correspondingdecrease in refrigeration requirements, and improved separation of wax from oil.

Example I ,In order to show the advantages of the process of the invention by 'specificzembo'dimentsg the present process was compared with the processof United States Patent Number 2,726,990.

According. to the process of the invention of said" patent, 520 barrels per' day of a petroleum distillate fraction and 960 barrels per day of a residual "fraction were processed, using 1100- barrels per day of wash,

liquid, to produce 1,180 barrels per day of oil. This and residual fractions were separately refined, dissolved in solvents, chilled 'to' about. -l0 F. and admixed only after chilling to precipitate wax for subsequent filtration;

This operation was substantially repeated,except that about 96 barrels per dayof distillate fraction were admixed withthe-residual'fraction, prior to dissolving the fractions in solvent for subsequent chilling to; about; 10 F., while maintaining the quantity of the distillate rate,.which was the limiting factor in the prior operation, easily handled the increased through-put so,.that about 1,260 barrels" of oil per day were produced and the filtra-a tion rate was not the limiting factor in the process 'i.e., an 7 even greater through-put could be maintained if desired. In theprocess, using the same quantities of solvent and" wash liquid, the oil content of the wax product is sub,-

stantially as inthe prior process, namely, about 15%.

are commercially available and are known to assist theseparation of wax 'from oil give good results. Such materials maybe condensation products, polymerization products, extracts from high boiling petroleum fractions, and: the like, such asdescribed in United States Paten 2,081,519, 2,178,328; and-2,722,499.

Good results are. obtained in'the process of the invent-ion when the ratio ofdistillate slurry to residual slurry, including the added distillate, is from 1:20 to 1 20:1, Which. I'-a1lO:11'1&y-'be. determined from the volumes 7 of the 'distillate and+residua1 fractions, ;or arm their rafi'inates ifrefined as in the examples herein given, or v fromthe-waxcontents thereo The foregoing desc1iption of 'the-process of thepresent invention hasbeen-.directed-'principally to-the dewa'xing 'of petroleumoila; The present process may alsobe employedwhere the primaryobject is to deoil wax to prepare wax-products; Forexample, the wax precipitate obtained asabove described,aor a slack wax containing 1 a relatively-large quantity of oil, say from about 10% to It'was found that. the'total amount of wash liquid could be reduced. to 800 barrels per day with an increase in 'oil. content of:the waxzto only about. 20%.

Example II In order to show the critical nature of the quantity of the distillate. fraction added to the'residual fraction. prior to chilling, and the advantages of using a filter aid, varying quantities of distillate fraction were introduced into the residual fraction,.a'nd' from about 0.026, to- 0.7% of a filter aid added to'the residual fraction. The filter. aid 7 was a commercially available hydrocarbon material'.de-.

rived from the high boiling petroleum' fraction.- The V I.

Ifollowingresults were obtainedz a 7 V I Adding 3.5% by volume of distillate fraction (based on the quantity ofthei residual fraction). to the-residual ction resultediin no. measurable increase. in the: rate of filtration, i.e., the total throughput wasnot increased.

I Adding.5% of the distillate fraction to the residual frao 60%, may be deoiled by subjecting theoilyfwa'x to a' V seriesbf stepshs above described. Forexample, a slack wax containing about 30% oil is subjected tovacuum tion resultedin a marked. increase inthe rate of'filtratioir which increased so that when'7% of distillate was added to the residual fraction, an additional 50 barrelsper dayof charge was-processed. Addition of even larger quana tities proved advantageous and the addition of 11% of distillate to.th'e residual fraction resulted in an increase inthefiltrationrate so that anadditional barrels:per f dayioffcharge. wass'processed. Aastill further increase ingthe filtration rate is observed up to about 15% of distillate in the residual fraction. However, introducing more than 20% of the distillate fraction into the residual fraction results in deleterious effects including an increase of the oil content of the slack wax product and a decrease in the rate of slack wax production. In all of the runs having from 5% to 20% by volume distillate in the residual fraction, the oil content of the wax remained at about 15%. the oil content of the slack wax increases to about 20%.

The invention claimed is:

1. Method of separating Wax from oil which comprises: (A) distilling a mixture of wax and oil to form at least two wax-oil fractions having different boiling ranges, (B) admixing a portion of the lower boiling fraction prior to any dewaxing thereof, with the higher boiling fraction, said portion being from 5% to 20% by volume based on the higher boiling fraction, (C) dissolving the remainder of the lower boiling fraction in a solvent and chilling the resulting solution to precipitate at least of the wax present whereby a slurry is formed, (D) dissolving the admixture of lower boiling fraction and higher boiling fraction in a solvent and chilling the resulting solution to precipitate at least 10% of the wax present whereby a slurry is formed, (E) admixing said slurries, (F) filtering the admixed slurries to separate said precipitated wax from oil and solvent, and (G) separating oil from solvent.

2. Method of separating wax from oil which comprises: (A) distilling a mixture of Wax and oil to form at least two wax-oil fractions having diiferent boiling ranges, (B) admixing a portion of the lower boiling fraction prior to any dewaxing thereof, with the higher boiling fraction, said portion being from 5% to 20% by volume based on the higher boiling fraction, (C) dissolving the remainder of the lower boiling fraction in a solvent and chilling the resulting solution to precipitate at least 10% of the wax present whereby a slurry is formed, (D) dissolving the admixture of lower boiling However, when the filter aid is omitted,

fraction and higher boiling fraction in a solvent and chilling the resulting solution to precipitate at least 10% of the wax present whereby a slurry is formed, (E) admixing said slurries in a volume ratio of slurry from the lower boiling fraction to slurry from the higher boiling fraction of from 1:20 to 20: 1, (F) filtering the admixed slurries to separate said precipitated wax from oil and solvent, and (G) separating oil from solvent.

3. Method of dewaxing petroleum oil which comprises: (A) distilling wax-bearing petroleum oil to form a distiilate Wax-oil fraction boiling in the range of from about 700 F. to about 850 F. at atmospheric pressure and a residual wax-oil fraction boiling above about 850 F. at atmospheric pressure, (B) admixing a portion of the distillate fraction, prior to any dewaxing thereof, with the residual fraction, said portion being from 5% to 20% by volume based on the residual fraction, (C) dissolving the remainder of the distillate fraction in a solvent and chilling the so-formed solution to a temperature of about -10 F. to precipitate at least 10% of the wax present whereby a slurry is formed, (D) dissolving the admixture of distillate and residual fractions in a solvent and chilling the so-formed solution to a temperature of about -10 F. to precipitate at least 10% of the wax present whereby a slurry is formed, (E) admixing said slurries, (F) filtering the admixed slurries at a temperature of about -l0 F. to separate precipitated wax from oil and solvent, and (G) separating oil from solvent.

References Cited in the file of this patent UNITED STATES PATENTS 1,963,498 Lord June 19, 1934 2,193,767 Manley et a1 Mar. 12, 1940 2,234,916 Jones Mar. 11, 1941 2,571,752 Overbaugh Oct. 16, 1951 2,666,730 Storment Jan. 19, 1954 2,726,990 Baker Dec. 13, 1955 2,780,581 Macke et al. Feb. 5, 1957

Claims

1. METHOD OF SEPARATING WAX FROM OIL WHICH COMPRISES: (A) DISTILLING A MIXTURE OF WAR AND OIL TO FORM AT LEAST TWO WAX-OIL FRACTIONS HAVING DIFFERENT BOILING RANGES, (B) ADMIXING A PORTION OF THE LOWER BOILING FRACTION PRIOR TO ANY DEWAXING THEREOF, WITH THE HIGHER BOILING FRACTION, SAID PORTION BEING FROM 5% TO 20% BY VOLUME BASED ON THE HIGHER BOILING FRACTION, (C) DISSOLVING THE REMAINDER OF THE LOWER BOILING FRACTION IN A SOLVENT AND CHILLING THE RESULTING SOLUTION TO PRECIPITATE AT LEAST 10% OF THE WAX PRESENT WHEREBY A SLURRY IS FORMED, (D) DISSOLVING THE ADMIXTURE OF LOWER BOILING FRACTION AND HIGHER BOILING FRACTION IN A SOLVENT AND CHILLING THE RESULTING SOLUTION TO PRECIPITATE AT LEAST 10% OF THE WAX PRESENT WHEREBY A SLURRY IS FORMED, (E) ADMIXING SAID SLURRIES, (F) FILTERING THE ADMIXED SLURRIES TO SEPARATE SAID PRECIPITATED WAX FROM OIL AND SOLVENT, AND (G) SEPARATING OIL FROM SOLVENT.