US2850431A

US2850431A - Solvent deasphalting

Info

Publication number: US2850431A
Application number: US556496A
Authority: US
Inventors: Smith Randlow
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1955-12-30
Filing date: 1955-12-30
Publication date: 1958-09-02
Anticipated expiration: 1975-09-02

Description

Sept. 2, 1958 R. SMITH soLvENT DEASPHALTING Filed Deo. so, 1955 soLvaNr unasrnar'rnso Randlow Smith, New Rochelle, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application December 3l), 1955, Serial No. 556,496

s claims. (ci. 19e-14.45)

This invention relates to the treatment of asphaltic oils with a deasphalting solvent for the separation of asphaltic constituents therefrom. More particularly, this invention is concerned with the treatment of asphaltic residual hydrocarbon oils for the recovery of asphaltic constituents therefrom and for the production of a deasphalted oil suitable for use as a catalytic cracking feed stock. In accordance with one embodiment, this invention relates to a process for deasphalting residual hydrocarbon oils for the production of an asphalt fraction and a deasphalted oil fraction which is subsequently solvent relined for the preparation of a catalytic cracking feed stock characterized by a relatively low metals content.

It is an object of this invention to provide an improved solvent deasphalting process.

It is another object of this invention to provide an improved solvent deasphalting process employing a volatile deasphalting solvent, such as a normally gaseous hydrocarbon, e. g., ethane, propane, n-butane, isobutane, npentane, isopentane and mixtures thereof, wherein the deasphalting solvent after having been employed to separate asphaltic constituents from the asphaltic oil undergoing treatment is recovered in a deasphalting solvent recovery system which does not require the use of compressors to effect liquefaction and recovery of the deasphalting solvent.

lt is another object of this invention to provide animproved and economical method for the recovery of deasphalting solvent employed in an operation involving the solvent deasphalting of aspha'ltic residual hydrocarbon oils.

How these and other objects of this invention are accomplished will become apparent with reference to the accompanying disclosure and drawing wherein there is schematically illustrated an embodiment of the practice of this invention directed to the solvent deasphalting of an asphaltic residual hydrocarbon oil. In at least one embodiment of this invention at least one of the foregoing objects will be achieved.

In accordance with this invention an asphaltic oil is solvent deasphalted by Contact with a deasphalting solvent under deasphalting conditions of temperature and pressure to effect separation of asphaltic constituents from said oil. There is recovered from the aforesaid deasphalting operation a liquid deasphalted oil phase having a reduced amount of asphaltic constituents and containing a portion of said deasphalting solvent and a liquid asphalt phase containing another portion of said deaspha-lting solvent. The deasphalted oil phase at substantially the deasphalting conditions of temperature and pressure is partially volatlized or vaporized, as by pressure reduction, to produce a resulting first liquid phase and a resulting first vapor phase containing deasphalting solvent at a temperature T1 and at a pressure P1. The resulting rst liquid phase is further treated, e. g., partial vapon'zation by pressure reduction, to produce a resulting second liquid phase comprising deasphalted oil and a resulting second vapor phase comprising deasphalting solvent at a tem' perature T2 and a pressure P2, T2 being lower than T1 and P2 being lower than P1. The aforesaid iirst and second vapor phases are then passed in indirect heat exchange relationship to each other whereby the temperature of said first vapor phase is reduced such that the vapor pressure of the deasphalting solvent therein is substantially lower than P1, preparatory to or leading to the ready liquefaction and condensation of the deasphalting solvent in said first vapor phase. The resulting second vapor phase after heat exchange with said vapor phase is then cooled to a temperature sufficiently low to effect condensation of the deasphalting solvent therein. By operating in accordance with the above-broadly-indicated method the deasphalting solvent contained in the deasphalted liquid oil phase issuing from the solvent deasphalting operation is substantially completely recovered in liquid form without requiring the use of compressors and the like and is available for recycle to the solvent deasphalting operation. Also by operating a solvent deasphalting operation in accordance with the above-indicated method, substantial heat economy is possible.

Referring now in detail to the drawing a reduced crude, such as a mixture of reduced California crudes, having an initial boiling point greater than about 650 F., usually having a boiling point greater than about 800 F., amounting to about 35-75% by volume of the original crude, is supplied via line 11 to vis-'breaker 12 where it is subjected to temperature, pressure and throughput conditions so as to mildly lower the viscosity of the reduced crude. A temperature in the range SOO-1000 F. and a pressure in the range 50-800 p. s. i. g. are usually sucient to eect mild vis-breaking of the reduced crude.

Vis-breaking of the reduced crude serves to reform or otherwise alter some of the high molecular weight or high boiling constituents of the reduced crude into relatively low molecular weight or low boiling constituents. The vis-breaking operation tends to produce lower boiling, more aromatic constituents which are generally more refractory in a catalytic cracking operation than lower boiling, more parah'inic hydrocarbons which are also produced. The vis-breaking operation complements and otherwise cooperates with a subsequent combination of deasphalting and solvent relining operations described hereinafter. The vis-breaking operation increases the yield of naphtha recoverable from the reduced crude in that the relatively more aromatic hydrocarbons produced during the vis-breaking operations are separated in a subsequent combination of fractionation, and deasphalting and solvent refining steps with the resulting production of a more parainic catalytic cracking charge stock suitable for the production of a catalytic cracked naphtha.

The mildly vis-broken reduced crude from vis-breaker 12 is introduced via line 14 into fractionator or atmospheric flasher 15 from which there is recovered overhead via line 16 a gas fraction comprising normally gaseous hydrocarbons such as propane and the butanes, a naphtha fraction via line 18, such as a 430 F. end point naphtha, and a gas oil fraction via line 19. There is also recovered from flasher 15 a bottoms fraction via line 20, The flasher bottoms is then introduced via line 20 into vacuum still or distillation zone 21 where it undergoes further fractionation for the production of a light gas oil fraction recovered via line 22 and a heavy gas oil fraction recovered via line 24. Vacuum bottoms is recovered from vacuum still 21 via line 25.

The vacuum bottoms fraction recovered from Vacuum still 21 via line 25, usually having a gravity A. P. l. in the range 3-12 and a Conradson carbon residue in the range 15-40%, more or less, is introduced via line 25 into the upper part of solvent deasphalting tower or zone 26. The solvent deasphalting operation may be a batch operation, a multiple vessel operation or a substanl isobutane.

Vtially continuous vliquid-liquid counter-current treating operation, as indicatedv inthedrawing, wherein thevacuum bottoms to be deasphalted is introduced via line 25 into the top of deasphalting tower 26 and flowed from deasphalting solventstorage tank-128;A A

' A suitable deasphalting -solvent-in accordance witlthe practice of this invention is a liqueed normally gaseous n hydrocarbon such' as ethane', ethylene, propane, propyl ene, normaly butane, isobutane, n-butylene, isobutylene, pentane, isopentane and mixtures'thereof, either aloney terials to improve-the deasphaltingV operation or otherwise increasethe` yield-and quality of the deasphalted oil and/orthe recovered asphalt.

ing adjusted so as to maintain the deasphalting solvent Vin the liquid phasev during the deasphaltingoperation.

A deasphalting temperature in the range G-325 F.,

usually-not-rnore than 75 degrees Fahrenheit'lower thano the critical temperature of the deasphalting solvent, and

a pressurefintherange G-800 p. s. i. g.,are employedv depending upon the composition of the deasphalting solvent employed and to Ysome extent the composition of the vacuum bottoms undergoing deasphalting. Generally, a deasphaltingsolvent to vacuum bottoms volume chargeratio in theV range 2-10 is employed within dea'sphaltirlg,tower4 w26.- Deasphalting tower 26 may beA operatedrrunder substantiallyisothermal conditionsV or under 'a temperature gradient, e. g., top tower temperatm-e5' greater'4 thanbottomtower temperature by not moreA than-about'40 degrees-Fahrenheit. Also deasphalting tower-26 may be operatedso that the vacuum bottoms is introduced thereinto at a number of points along the height of the towerYand/or so that the deasphalting solvent is-introduced thereinto at a number ofpoints.

Following ythe deashpalting operation there is recovered from 'deasphalting tower 26 a deasphalted oilv solventi mix via line 31 andan asphalt solvent mix via`lin'e' 3,0.

The deasphalted oil in themix in line 31 may have' a gravityV A; P.- I. in the range 10-25` and a Conradson carbon residue in the range l-l0% and a viscosity inthe range 20G-60G SUS at 210 F., more or less. The deasphalted oil solvent transferred from line 31 viav llne 32 through a vaporizing device, such as pressure tially vaporized to a lower temperature` andpressurethan the temperature and pressurepreva'iling-in lineV 381 The resulting partially vaporized rst liquid'phase is then passed .in indirect counter-current heat exchangerelatonship via lines 41a, 41b and 41e by means of -heatv exchangers 42a, 42b and 42C vwith said tirst vapor phase in-A troduced into the heat exchangers via lines,44a, 4412 and 44C, respectively. After the above-described lieat eX- change has taken place the resulting partially vaporized lirst liquid phase is recovered via linel 45 and introduced into deasphalted oil flashldr'um'. The resulting cooled, rstr vapor phase, 'approaching the temperatureV of theA partially vaporized rst' liquid phase inlinesl 41a, 4'1by and' 41e, is recoveredvia line 48 and, if necessary, after` having been cooled in' cooler 49" is introduced into deasphalting solvent storage tankiZS from which the resultl The deasphalting operation is` carried out vat any suitable deasphalting tem-4 perature and pressure, the temperature and pressure be- 15 or in admixturewith a' minor amount of additive maf ill ing liquelied deasphalting solvent can be returnedto deasphalting-tower 26 via line 29.l

The partially vaporized first liquid phase introduced into deasphalted oil ash drum 46 via line 45 is separated into an overhead solvent vapor phase via line 51 comprising substantially only deasphalting solvent and a liquid oil phase via line S24 comprising substantially only deasphalted oil. The deasphalting solvent vapor phane in line 51' iscooled in cooler 54 Iandthe resultmg liquefied deasphalting solvent is passed. via lines 55andf 56 into deasphaltingsolvent storage tank 58.`

The liquid asphalt deasphalting solvent mix leaving deasphalting tower 26 is passed via line 30v through a heater'59 and line 60r into asphaltilasher 61'. Theresulting vaporized deasphalting/solvent is removed overhead rorn asphalt asher 61 via line 62 for introduction into deasphalted oil ash drum 46 for the eventual liquefaction and recovery Vof the deasphalting solvent as indicated hereinabove; There is removed from asphalt asher 61 a liqued asphalt bottoms via line 64"wh`ich` is introduced'into asphalt stripper 65ifor the removal' overhead vialine 66 of residual deasphalting' solvent by the injection of'high temperature,' high pressure steam v into asphalt stripper 65via liner68. The resulting steam' stripped asphalt is removed as liquid bottoms from asphalt asphalting solvent removed from asphalt stripper 65Y via' line 66 is introduced into the upper portion of deasphalted oil stripper 70 wherein it is admixed with the deasphalted oil bottoms removed from deasphalted oil dash drum 46 via' line 52. High pressure", high temperature' steam is introduced into the lower portion of deasphaltedoil stripper 70 via line 71 and there Vis removed overhead from oil stripper 70 via line 72 a vaporous admixture of deasphalting solvent andv steam.' This vaporous admixture iscooled in cooler74'to a temperature suciently low to condense or liquefy substantially all of the deasphalting solvent and steam present in theadmixture, e. g., cooled to a temperature about 100 F. and lower. The resulting cooledv admixture is then introduced via line 75* into water separator 76' fromV which water condensate is removed via line 78 andthe resulting condensed liqueed deasphalting solventV is removed, via

lines

79 and 56 into deasphalting solvent storagetank 58 or'reuse in thedeasphalting operation. I f necessary or'desired', the liquid deasphalting solvent in storage. tank' 58' can be employed via

lines

80 and 81 to' supplement the deasphalting solvent in deasphaltingV solvent storage tank 28.

Referring now to thegas oil fraction recovered from atmospheric a'sher 15 via line 19, this gas oil fraction is' introduced into topping still S2 where there is produced overheadvia line 84 a 500ml?. end point naphtha fraction particularly suitable as a catalytic cracking,

charge stock.' Theb'ottoms fraction recovered from topping still.82 via line 85 is combined therein with the gas oil fractions' removed from vacuum still 21`via lines 22, 24 and'95.

The deasphalted oil recoveredy from deasphalted oil stripper 70 via linel 86 after coolingV in cooler 884 is introduced via line 89 into pretreater. 90'wherein it is conl tacted with aoliquid selective solvent'for aromatic hydrocarbons, such'v as fui-tural. Pretreater 90 may be any suitable device for electing liquid-liquid contactV be-y tween the liquidselective solvent` employedand the de,-V asphalted oilfbeing pretreated. Preferably pretreater 9G is an apparatus suitable for effectingcontinuous countercurrent liquid-liquid contact, suchL as at packed tower, a centrifugal contactor or arotating disc contactor.. lf desired, there'may be blended or` otherwise admixed with thedeasphaltedoil introduced via linei89'intorpretreater 9fadded deasphalting solvent introducedvialine Si) into admixture with` the deasphalted oilin line 89; The; de-

asphalted` oily introduced. via` lineA S9; intofpretreater mais' contacted therein with a solvent extract mix comprising selective solvent, such as furfural, together with the dissolved hydrocarbons therein, which is recovered from solvent refining unit 91, described hereinafter, and introduced into pretreater 90 via line 92. The resulting deasphalted oil raffinate from pretreater 90 is recovered via line 94 and introduced into line 85 for introduction into selective solvent refining unit 91 in admixture with the bottoms fraction recovered from topping still S2 and the gas oil fractions removed from vacuum still 2l via lines 22, 24 and 95. if desired, liquid deaspA solvent from deasphalting solvent storage tank 53 may be admixed via lines Si) and Q6 with the pretreated deasphalted oil prior to introduction into selective solvent refining unit 91. Also, if desired, a portion of the deasphalted oil solvent mix recovered from deasphalting tower Z6 via line 3i may be introduced via line 95 into line 35 for eventual admixture with the pretreated deasphalted oil in selective solvent refining unit 91.

The resulting extract eflluent from pretreater 43 is recovered via line 93 and introduced into selective solvent recovery unit $9 wherein the selective solvent, e. g., furfural, is recovered and recycled to selective solvent rening unit 9i via line lili). The resulting separated extract is recovered from selective solvent refining unit 99 via line itil. Various selective solvents may be employed in selective solvent rening unit 9i, these include furfural, phenols (Selecto), nitrohervene, sulfur dioxide, ,'dichloroethyl ether (Chlo-rex), dimethyl formamide and other selective solvents for aromatic hydrocarbons.

The resulting admixture in line 3S comprising the bottoms fraction from topping still SZ, the gas oil fractions from vacuum still 2i, selective solvent pretreated deasphalted oil from pretreater Sti and, if desired, the liquid deasphalting solvent recovered from deasphalting solvent storage tank 5S via lines Si) and 9d or a portion of the deasphalted oil-deasphalting solvent mix recovered from deasphalting tower 26 via lines 3i and 95, is introduced into selective solvent refining unit 9i wherein it cws in liquid-liquid counter-current contact with a liquid selective solvent, such as furfural, which selectively dissolves or extracts the more aromatic hydrocarbons therefrom. As previously indicated, the resulting extract mix from selective solvent refining unit 9i comprising selective solvent and extracted hydrocarbons is recovered via line 92 and introduced into pretreater 9i).

The aromatic type hydrocarbons contained in the extract mix introduced into pretreater 9u via line 92 and employed to Contact and pretreat the deasphalted oil introduced thereinto via line 39 further increase the solvent power of the selective solvent for the metal-containing components in the deasphalted oil being thus pretreated and thus assist in the removal of these metal-containing components (the presence of which is undesirable in a catalytic cracking charge stock) from the deasphalted oil. Furthermore, since the concentration of the metal-containing components would be greater in the deasphalted oil than in the admixture in line 85 introduced into selective solvent refining unit 9i a greater overall degree of metals removal is possible. Also, the selective solvent contained in the deasphalted oil rainate recovered from pretreater Si@ via line 94 serves to predilute the deasphalted oil ra'l'lnate introduced in admixture with the gas oils and bottoms fraction via line into selective solvent refining unit This predilution of the feed to the selective solvent reiining unit 9i increases the eiciency of the selective solvent refining operation therein, Still further, the deasphaltcd oil introduced into pretreater 9d via line 8g' removes from the extract mix introduced thereinto via line 9i. the lower molecular weight, more paraiiinic hydrocarbons therein which may have been taken into solution in the extract mix during the refining of the combined feed admixture supplied to the selective solvent rening unit 9i via line d5. These more paratiinic mad terials are returned continuously to the selective solvent refining unit 9i and thus the overall yield of the rafnate recovered from selective solvent refining unit 9i via line l'lZ is increased. The contacting or scrubbing of the extract mix within pretreater 9&9 should result in a reduction in the quantity of the more paraflinic materials withdrawn from pretreater 9i) as solvent elfluent via line 98 and eventually removed from the system as extract suitable as cutter stock via line itil.

The raffinate removed from selective solvent refining unit via line to2 having a reduced metals content, e. g., vanadium, nickel, copper, iron and similar heavy metals, in the range 0.2-5 p. p. m., after having been freed of its selective solvent content is combined via line 8d with the 560 F. end point naphtha fraction recovered from topping still 82 and introduced as feed stock to fluid catalytic cracking unit ldd where it is contacted with iuidized cracking catalyst.

A cracking catalyst usually comprises an oxide of metals of groups ll, lll, IV and V of the periodic table, for example, a silica-alumina catalyst containing about 540% by weight alumina. The average particle size of the cracking catalyst particles is usually below about 200 microns, a size sufficient to produce a dense fluidized bed of cracking catalyst.

The resulting cracked catalyst ellluent from iluid catalytic cracking unit illis introduced via line M5 into fractionator ldd wherein it is fractionated into a catalyic cracked naphtha recovered via line 16S, a catalytic cracked light gas oil recovered via line lil@ and a relatively heavy cycle gas oil, e. g., FCCU decanted oil, recovered via line llt).

To the asphalt recovered from asphalt stripper 65 via line 69, which asphalt may have a ring and ball softening point in the range l325 F., is added at least a portion of the gas oil fractions recovered from catalytic cracking fractionator 106 via lines 109, il@ and 111 and at least a portion of the selective solvent-free extract recovered from selective solvent recovery Zone 99 via line itil, the resulting stream of combined catalytic cracked gas oils and selective solvent extract being added via line lll as cutter stock to the asphalt in lin-e 69.

lf desired, at least a portion of the catalytic cracked light gas oil recovered from fractionator M6 via line 109 and/or the heavy gas oil or FCCU decanted oil recovered via line 110 `are passed via lines lll and 89 to pretreater 9'@ or in admixture via

lines

112 and 35 to selective solvent refining unit 91 for the recovery of the more parainic constituents therefrom as raffinate via line 5102 to provide additional catalytic cracking charge stock and for the eventual recovery of the more aromatic constituents therefrom as extract via line Still as cutter stock. When the gas oil recovered from catalytic cracking fractionator 1%, such as the PCSU decanted oil, possesses a relatively high metals content, e .g., more than about 30 p. p. m. heavy metals, the gas oils are preferably introduced via lines lll and 39 as feed to pretreater in order to reduce its metals content.

Pretreater 9d is operated at any suitable temperature and pressure for effecting liquid-liquid contacting and for the removal of the more aromatic components contained in the feed thereto. The operating conditions and solvent dosages employed within pretreater 99 are influenced to some extent by the composition of feed thereto and the type of selective solvent employed therein. ln the instance where furfural is employed as the selective solvent pretreater 9d is operated at a solvent dosage in the range 75-250%, e. g., 125%, basis oil charge whereas selective solvent refining unit 9i, employing the same solvent (furfural), might be operated at a relatively lower solvent dosage in the range l0l00%, e. g., about 25 basis oil charge thereto. By operating in accordance with this feature of the invention the yield-of recoverable catalytic cracked naphthais further increased.

Cutback product asphalt is recovered via line 114. Desirably, however, especially when a heavy crude such as a San Ardo, California,-crude is the source of the reduced crude introduced into the above-described operations via line 11, the asphalt in line 69, prior to the addition of cutter stock thereto via line 111, is subjected to vis-breaking as indicated by asphalt vis-breaker 115 in the drawing `and the cutter stock added to the resulting vis-broken asphalt via line 111:1. The resulting cutback vis-broken asphalt is then removed as product via line 118. Desirably a'portion of the combined stream employed as cutter stock in line'111 is admixed via line 116 with the solvent asphalt mix recovered from deasphalting tower 26 via line 30 prior to introducing the same into asphalt heater 59. This addition of cutter stock to the asphalt deasphalting solvent mix prior to introduction into asphalt heater 59 is desirable in order to alleviate coke deposition and reduce cracking which might otherwise occur within the furnace heating tubes and upon the heated surfaces within the asphalt-deasphalting solvent recovery system.

The following is illustrative of the practice of this invention. A mixture comprising California crude Was atmospherically distilled to about 50-55% volume reduced crude based on the original crude mixture and charged through a heater operated under mild viscosity breaking conditions at an outlet temperature of 850 F. The resulting mildly viscosity broken reduced crude was introduced into an atmospheric flasher from which was recovered overhead approximately 46% total volume yield of gas oil, naphtha yand atmospheric viscosity broken gas oilbasis reduced crude, in the following amounts: gas 1% volume; 430 F. end point naphtha 3.5% volume; gas oil 41.5% volume, the atmospheric asher being operated at a maximum temperature of about 790-800 F. The atmospheric flasher bottoms having a gravity of about 12 A. P. I. and a Conradson carbon residue of about 15 was introduced into a vacuum still operated at about 25 mm. Hg at a temperature of 665 F. There wasrecovered overhead from the vacuum still gas oil fractions amounting to about 42% by volume of the vacuum still charge and a heavy bottoms fraction amounting to about 16% by volume basis-V original crude mixture or about 33.8% volume basis re- Table No. I

Deasphalting Deasphalted oil Solvent Temp., Press., Yield, Carbon P.p.m. P.p.m. P.p.m F. p.s,i g, weight residue, Fe Ni V percent percent Charge-.- 26 80 150 350 Isobutane.- 200 230 46. 5. 9 6 1l 9 D0.-.. 235 335 40.1 5.0 6 8 5 D0. 245 385 42. 0 4. l Do 270 475 35.6 3.0V 8 3 3 There was directly recovered) from a deasphalting operation carried out in the-manner described hereinabove a liquid deasphalting solvent-deasphalted oil mix containing. deasphalted. oil and isobutane at a temperature of. about 248 F. and. at a1 pressure of about 3'90' p. s. i. g.; there was also directly recoveredV a liquidabout 390 p. s. i. g. w-as partially vaporized by passage through an expansion valve to yield a first vapor phase at a temperature of about 190 F. and at a-pressure ofI at least about 175 p. s. i. g., e. g., about 210 p. s. i. g., and a first liquid' phase at substantially the same temperature and pressure as said first vapor phase. first liquid phase is then partially vaporized by passage through an expansion valve to yield `a partially liquefied admixture containing deasphalted oil and vaporous isobutane at a temperature of about 145 F. and at a pressure of at least about p. s. i. g., preferably aboutV 100l p. s. i. g. The resulting vaporous admixture is then passed in indirect heat exchange relationship with said rst vapor phase to yield a resulting relatively cooled first vapor, phase at a temperature in the range 190- 200" F. (at a pressure about 205 p. s. i. g.) whereby the isobutane deasphalting solvent in said first vapor phase is condensed and liqueed or is readily condensedand liquefied by supplemental cooling to a temperature. of about 190 F. the pressure in the resulting cooled first vapor phase being at least about 160 p. s. i. g. and

higher if necessary in order to eiect liquefaction of the. The resulting admixtureisobutane deasphalting solvent. of liquid deasphalted oil and vaporous isobutane-derived from first said liquid phase, after having been passed in indirect heat exchange relationship -with said rst vapor phase, now at a temperature of about 160 F. and is passed to a gas liquid separator from which there is recovered overhead, at a pressure of about 100 p. s. i. g., vaporous isobutane which is liquefied and condensed by cooling to a temperature of about 126 F. at a pressure of atleast about p. s. i. g. The separated deasphalted oil is then steam stripped to effect substantially complete removal of isobutane therefrom and the resulting steam stripped isobutane is recovered by cooling theeluent resulting from the steam stripping operation toy a temperature of about 90-100 F., more or less, at a pressure of at least about 50 p. s. i. g., preferably above about 75 p. s. i. gr. and at least sucient to effect liquefaction of the deasphalting solvent at said temperature, and passed to storage at a temperature of about 126 F. at a pressure of about 95 p. s. i. g.

The deasphalted oil recovered from a solvent recovery operation described hereinabove has a gravity in the range 15.3-16.8 A. P. I., a viscosity SUS 210 F..iu the range 23S-281 and a K factor of about 11.7.

The liquid asphalt deasphalting solvent mix phase containing asphalt adniixed with isobutane, afterr the addition of an amount of cycle gas oil cutter stock, is passed to the asphalt heater and heated to .a temperature Y,of about 500 F. at a pressure of about 100 p. s. i. g.

The resulting heated asphalt-isobutane stream was passed to an asphalt separator from which there is recovered overhead vaporous isobutane which is admixed with vaporous isobutane from the deasphalted oil ash drum, from which admixture liquid isobutane is condensed by cooling the resulting vaporous stream to a temperature of about 126 F. at a pressure preferably at least about A high boiling petroleum fraction comparable to the-` deasphalted oil recovered from the asphalt deasphalting operation is subjected to liquid-liquid contact with furfural solvent extract mix at a solvent dosage in the range -20,0% volume, e. g., 125%, basis oil charge,

the furfuralv solvent extract mix having been derivedv The liquid deasphalted oil-isobutane The from the furfural solvent refining of the resulting deasphalted oil raffinate in admixture with VPS gas oil, said subsequent furfural resing being carried out at a solvent dosage in the range 15-75%, basis oil charge. The rainate resulting from the subsequent furfural rening operation possesses a significantly lower metals content, substantially below 3G p. p. m., in the range 5-20 p. p. m. and lower.

It is also advantageous in the practice of this invention to carry out the subsequent solvent rening operation and/or the selective solvent pretreatment of the deasphalted oil in the presence of a substantial amount of a light liquid hydrocarbon, such as the deasphalting solvent, in an amount in the range lf3-200% volume, more or less, based on the deasphalted oil charged to the pretreater or to the selective solvent refining unit. By so operating the metals content of the resulting raffinate (selective solvent refined deasphalted oil) is -further reduced, e. g., below about 5 p. p. m. The advantages of carrying out a solvent refining operation in the presence of a liquid low molecular weight hydrocarbon, e. g., deasphalting added thereto or present in the deasphalted oil due to the incomplete removal of deasphalting solvent therefrom is more completely set forth in copending, coassigned patent application Serial No. 547,638, filed November 18, 1955. Also the advantages of carrying out a solvent refining operation by pretreating a deasphalted oil by contact with a solvent extract mix and then subjecting the resulting pretreated deasphalted oil to contact with fresh selective solvent in a selective solvent refining unit in order to produce a suitable catalytic cracking charge stock is more completely set forth in copending, coassigned patent application Serial No. 555,495, filed December 30, 1955. The disclosures of the above-referred patent applications are herein incorporated and made part of this disclosure.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many substitutions, changes and alterations are possible in the practice of this invention without departing from the spirit or Scope thereof.

I claim:

l. A method of treating an asphaltic oil which cornprises contacting said oil with a deasphalting solvent under deasphalting conditions of temperature and pressure to effect separation of asphaltic constituents from said oil, recovering from the aforesaid operation a liquid oil phase having a reduced amount of asphaltic constituents and containing a portion of said deasphalting solvent and a liquid asphalt phase containing another portion of said deasphalting solvent, treating said liquid oil phase to produce a resulting first liquid phase and a resulting rst vapor phase comprising deasphalting solvent at a temperature T1 and at a pressure P1, treating said first liquid phase to convert the same to a resulting second liquid phase and a resulting second vapor phase comprising deasphalting solvent at a temperature T2 and a pressure P2, T2 being lower than T1 and P2 being lower than P1, passing said first vapor phase and second vapor phase in indirect heat exchange relationship to each other whereby the temperature of said first vapor phase is reduced such that the vapor pressure of the deasphalting solvent therein is substantially reduced, `condensing deasphalting solvent from said first vapor phase, heating said liquid asphalt phase to produce a third vapor phase comprising deasphalting solvent and a third liquid phase comprising asphalt, admixing said third vapor phase with said second vapor phase `after said second vapor phase has been passed in indirect heat exchange relationship with said first vapor phase, recovering the resulting combined second and third vapor phases and cooling the resulting combined second and third vapor phases to a temperature suficiently low to condense the deasphalting solvent therein.

2. A method of treating an asphaltic oil which comprises contacting said oil with a deasphalting solvent under deasphalting conditions of temperature and pressure to effect separation of asphaltic constituents from said oil, recovering from the aforesaid operation a liquid oil phase having a reduced amount of asphaltic constituents and containing a portion of said deasphalting solvent and a liquid asphalt phase containing another portion of said deasphalting solvent, treating said liquid oil phase to produce a resulting first liquid phase comprising deasphalting solvent land a resulting first vapor phase comprising deasphalting solvent at a temperature T1 and a pressure P1, treating said first liquid phase to convert the same to a resulting second liquid phase and a resulting second vapor phase comprising deasphalting solvent at a temperature T2 and a pressure P2, T2 being lower than T1 and P2 being lower than P1, passing said rst vapor phase and said second vapor phase in the presence of said second liquid phase in indirect heat exchange relationship to each other whereby said first vapor phase is reduced to a temperature such that the vapor pressure of the deasphalting solvent is substantially reduced, condensing deasphalting solvent from said first vapor phase, heating said liquid asphalt phase to produce a third vapor phase comprising deasphalting solvent and a third liquid asphalt phase, -admixing said third vapor phase with said second vapor phase in the presence of said second liquid phase after said second vapor phase has been passed in indirect heat exchange relationship with said first vapor phase, recovering from the aforesaid admixing operation the resulting combined second and third vapor phases and said second liquid phase, cooling the resulting combined second and third vapor phases to a temperature sufficiently low to condense the deasphalting solvent therein, steam stripping the recovered second liquid phase to remove substantially all of said deasphalting solvent therefrom and recovering from the aforesaid steam stripping operation said second liquid phase comprising a deasphalted oil substantially free of deasphalting solvent.

3. A method of treating an asphaltic oil which comprises contacting said oil with a deasphalting solvent under deasphalting conditions of temperature and pressure to effect separation of asphaltic constituents from said oil, recovering from the aforesaid operation a 4liquid oil phase having `a reduced -amount of asphaltic constituents and containing a portion of said deasphalting solvent and a liquid asphaltic phase comprising another portion of said deasphalting solvent, treating said liquid oil phase to produce a resulting first liquid phase cornprising deasphalting solvent and a resulting first vapor phase comprising deasphalting solvent at a temperature T1 and a pressure P1, treating said first liquid phase to convert the same to a resulting second liquid phase and a resulting second vapor phase comprising deasphalting solvent at a temperature T2 and a pressure P2, T2 being lower than T1 and P2 being lower than P1, passing said first vapor phase and said second vapor phase in the presence of said second liquid phase in indirect heat exchange relationship to each other whereby said first vapor phase is reduced to -a temperature such that the deasphalting solvent therein is condensed, recovering the resulting condensed deasphalting solvent, heating said liquid asphalt phase to produce a third vapor phase comprising deasphalting solvent and a third liquid phase, admixing said third vapor phase with said second vapor phase in the presence of said second liquid phase after said second vapor phase has been passed in indirect heat exchange relationship with said first vapor phase, separately recovering from the aforesaid adrnixing operation the resulting combined second and third vapor phases and said second liquid phase, cooling the resulting cornbined second and third vapor phases to a temperature sufficiently low to condense the deasphalting solvent therein, steam stripping said third liquid phase to re- 11 moyesubStantially-all of said deasphalting solvent therefrom and. to` produce overhead a fourthuvapor phase comprising steam and deasphaltingsolvent, steam stripping the recoveredsecond liquid phase to remove suba. stantally al1 of; said deasphalting solvent therefrom andV to produce overhead a fth vapor phase comprising steam and-,vaporized deasphaltng solvent, recovering from the,

immediate aforesaid steam stripping operation'saidecond liquid phase comprising a deasphalted oil substantially free .of deasphalting solvent, admixing said,fourth` and, fth vaporA phases land cooling the resulting com- 'biuedvaplortol atemperat'ure suiciently low to condenseA theusteamvand deasphaltingl solvent contained in saidyadmixedsteam'and separately recovering. theresulting conde nsedA d easphalting solvent and condensed steam.

4. Ina ,process` wherein an asphaltic oil is treated with av de asphalting solvent under deasphalting conditions of temperature and pressure to separate asphaltic constituents fromsaid oil and wherein there is recovered from.

vat avtemperature lower than said iirst liquid phase and a secondliquid phase containing deasphalted oil, passingsaid rst vaporphase in indirect heat exchange relation;n ship with said second` vapor phasertoA substantially re-u duce the temperature of, said first vaporphase topmf duce aresulting rst vapor phase substantially saturated with respect to said deasphalting solvent and recovering; liquefied deasphalting` solvent resulting from `said first` vapor` phase.

5. A process in accordance with c lairnv '1` whereinA said deasphaltingV solvent` comprises isobutane.

6. A process in accordance with claim 4 whereby the pressure diierentialbetweensaid lower pressure zone and, said lowk pressure-zone is in the range of.50-20O p. s. i. g.,l

7. A process in accordance with claim 4.wherein the temperature of said resulting rstvapor phaseis a range 20-60 degrees Fahrenheit lower than first said.

vapor phase.

l 8. A method in accordance with claim 4Iwherejn the temperature of said first vapor phase ,after heat exchange,y is reduced to a value so that substantially al1 oftl1fe..

deasphalting solvent. therein is liquefied.

ReferencesV Cited in the iile of this patent UNT-IED STATES PATENTSl 2,121,517 Brandt June 21, 1938 2,192,253 Adams Mar. 5, 1940 2,223,192 Swartwood Nov. 26, 1940 2,383,535 Dickinson et al Aug. 28, 1945` 2,538,220 Willauer Jan. 16, 1951 2,645,596 Axe July 14, 1953`

Claims

1. A METHOD OF TREATING AN ASPHALTIC OIL WHICH COMPRISES CONTACTING SAID OIL WITH A DEASPHALTING SOLVENT UNDER DEASPHALTING CONDITIONS OF TEMPERATURE AND PRESSURE TO EFFECT SEPARATION OF ASPHALTIC CONSTITUTENTS FROM SAID OIL, RECOVERING FROM THE AFORESAID OPERATION A LIQUID OIL PHASE HAVING A REDUCED AMOUNT OF ASPHALTIC CONSTITUENTS AND CONTAINING A PORTION OF SAID DEASPHALTING SOLVENT AND A LIQUID ASPHALT PHASE CONTAINING ANOTHER PORTION OF SAID DEASPHALTING SOLVENT, TREATING SAID LIUQID OIL PHASE TO PRODUCE A RESULTING FIRST LIQUID PHASE AND A RESULTING FIRST VAPOR PHASE COMPRISING DEASPHALTING SOLVENT AT A TEMPERATURE T1 AND AT A PRESSURE P1, TREATING SAID FIRST LIQUID PHASE TO CONVERT THE SAME TO A RESULTING SECOND LIQUID PHASE AND A RESULTING SECOND VAPOR PHASE COMPRISING DEASPHALTING SOLVENT AT A TEMPERATURE T2 AND A PRESSURE P2, T2 BEING LOWER THAN T1 AND P2 BEING LOWER THAN P1, PASSING SAID FIRST VAPOR PHASE AND SECOND VAPOR PHASE IN INDIRECT HEAT EXCHANGE RELATIONSHIP TO EACH OTHER WHEREBY THE TEMPERATURE OF SAID FIRST VAPOR PHASE IS REDUCED SUCH THAT THE VAPOR PRESSURE OF THE DEASPHALTING SOLVENT THEREIN IS SUBSTANTIALLY REDUCED, CONDENSING DEASPHALTING SOLVENT FROM SAID FIRST VAPOR PHASE, HEATING SAID LIQUID ASPHALT PHASE TO PRODUCE A THIRD VAPOR PHASE COMPRISING DEASPHALTING SOLVENT AND A THIRD LIQUID PHASE COMPRISING ASPHALT, ADMIXING SAID THIRD VAPOR PHASE WITH SAID SECOND VAPOR PHASE AFTER SAID SECOND VAPOR PHASE HAS BEEN PASSED IN INDIRECT HEAT EXCHANGE RELATIONSHIP WITH SAID FIRST VAPOR PHASE, RECOVERING THE RESULTING COMBINED SECOND AND THIRD VAPOR PHASE AND COOLING THE RESULTING COMBINED SECOND AND THIRD VAPOR PHASE TO A TEMPERATURE SUFFICIENTLY LOW TO CONDENSE THE DEASPHALTIN SOLVENT THEREIN.