US2943050A - Solvent deasphalting - Google Patents

Description

June 28, 1960 D. K. lax-:AVON

soLvEN'r DEASPHALTING Filed Deo. 3, 1957 me x hs -another portion of said deasphalting solvent.

United States Patent O soLvENT DEAsPHALTlNG Beavon, Darien, Conn., assignor to Texaco Inc., a corporation of Delaware i David K.

This invention relates to the treatment of asphaltic oils by a deasphalting solvent for the separation of asphaltic constituents therefrom. More particularly, this invention is concerned with the treatment of asphaltic 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, the asphalt fraction being handled in a special manner in accordance with this invention to reduce corrosion and thermal cracking or coking.

Itis an object of this invention to provide an improved solvent deasphalting operation.

It is another object of this invention toprovide an improved solvent deasphalting process particularly suitable for handling hard asphalts.

'Still another object of this invention is to provide an improved solvent deasphalting operation wherein thermal cracking of the separated asphalt and/or corrosion resulting from thermal cracking of the separated asphalt is substantially reduced.

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 the oil. There is recovered from the aforesaid deasphalting operation a liquid deasphalted oil phase or mix comprising oil having a reduced amount of asphaltic constituents and a portion of said deasphalting solvent, and a liquid asphalt phase or mix containing asphalt and The liquid asphalt mix is then admixedwith a cutter stock such as `a petroleum fraction derivable from the deasphaltedv oil, .or the deasphalted oil itself, or a petroleum fraction having a boiling point or boiling point range substantially the same as or less than the deasphalted oil and passed :through an asphalt heater to increase its temperature to at least about 350 F., such as about 500 F. The resulting heated liquid admixture of deasphalting solvent, cutter stock and asphalt is then ashed in asphalt flasher and the resulting vapors, comprising substantially only thedeasphalting solvent and the cutter stock are recovered and introduced into the above mentioned liquid deasphalt'ed oil phase or mix. The hot vaporous admixlture of deasphalting solvent and cutter stock serves to heat 'the liquid deasphalterd o il mix and thereby better promote/sfthe vaporization and separation of this mix into solvent and a liquid phase comprising deasphalted oil together with the previously admixed cutter stock. By operating a solvent deasphalting operation in accordance with the above-indicated method substantial heat economy is possible.

The introduction of cutter stock into the liquid asphalt mix prior to passing the liquid asphalt mixthrough the asphalt heater obviates or substantially reduces the thermal cracking Aof the asphalt as it passes therethrough since the cutter stock serves to maintain the asphalt in a liquid condition and tends to prevent deposition of solid asphalt within the heater tubes. Should thermal cracking of the asphalt within the heater tubes occur asphalt and coke would tend to deposit therein leading to additional thermal cracking and coking. Further, due to thermal cracking hydrogen sulde is produced and the thus-produced hydrogen sulfide tends to corrode the heater tubes, leading to frequent tube failure and replacement. In addition, any hydrogen suliide thus produced would tend to accumulate in the deasphalting solvent and lead to corrosion problems in the various associated petroleumprocessing units. Accordingly, by admixing cutter stock with the liquid asphalt mix prior to the mix la vvz'apor'ph'ase comprising substantially only deasphalting.

passing through the asphalt heater coke deposition and corrosion is reduced and minimized. At the same time the hot vapors from the asphalt flasher, following the asphalt heater, serve to vaporize and effect a better separation of the liquid deasphalted oil phase or mix into its primary components, liquid deasphalted oil and vaporized deasphalting solvent.

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 n 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 800-1000 F, and a pressure in the range 50-800 p.s.i.g. are usually suflcient to effect mild vis-breaking of the reduced crude. l

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 producel lower boiling, more aromatic constituents which are generally more refractory in a catalytic cracking operation than lower boiling, more paranic 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 yieldof 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 parafnic catalytic cracking charge stock suitable for the production of a catalyticcracked naphtha. i

The mildly vis-broken reduced 4crude from vis-breaker 12 is introduced via line 14 into fractionator or atmospheric flasher 15 fromfwhich there is recovered'overhead via line 16 a gas fraction comprising normallyl 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 fractionl via line 20. The flasher bottoms is then introduced via line 20 into vacuum 'still' or distillation z one'21 where it ,undergoes further ffractionation for the production of a light gasoil fraction n Patented June 28, `196() l 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.

Thevacuum bottoms fraction recovered from vacuum still 21 via line 25, usually having a gravity A.P.I. in the range 3-12 and a Conradson carbonresidue in the range l-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 substantially continuous liquid-liquid countercurrent treating operation, as indicated in the drawing, wherein the vacuum bottoms to be deasphalted is introduced via line 25 into the top of deasphal-ting tower 26 and owed therein in countercurrent liquid-liquid contact with a suitable deasphalting solvent, such as a liqueed normally gaseous hydrocarbon, e.g., propane, n-butane, isobutane. The deasphalting solvent is introduced via line 29 into the bottom portion of deasphalting tower 26 from deasphalting solvent storage tank 2S.

A suitable deasphalting solvent in accordance with the practice of this invention is a liquefied normally gaseous hydrocarbon such as ethane, ethylene, propane, propylene, isopentane and mixtures thereof, either alone or in admixture with a minor amount of additive materials to improve t'ne deasphalting operation or otherwise increase the yield and quality of the deasphalted oil and/or the recovered asphalt. The deasphalting operation is carried out at any suitable deasphalting temperature and pressure, the temperature and pressure being adjusted so as t0 maintain the deasphalting solvent in the liquid phase during the deasphalting operation. A deasphalting temperature in the range 150-325 `F., usually not more than 75 degrees Fahrenheit lower than the critical temperature of the deasphalting solvent, and a `pressure in the range 20G-800 p.s.i.g., are employed depending upon the composition of the deasphalting solvent employed and to some extent the composition of the vacuum bottoms undergoing deasphalting. Generally, a deasphalting solvent to vacuum bottoms volume charge ratio in the range 2-10 is employed within deasphalting tower 26. Deasphalting tower 26 may be operated under substantially isothermal conditions or under a temperature gradient, e.g., top tower temperature greater than bottom tower temperature by not more than about degrees Fahrenheit. Also deasphalting tower 26 may be operated so that the vacuum bottoms is introduced thereinto at a number of points along the height of the tower and/or so that the deasphalting solvent is introduced thereinto at a number of points.

Following the deasphalting operation there is recovered from deasphalting tower 26 a deasphalted oil solvent mix via line 31 and an asphalt solvent mix via line 30. The deasphalted oil in the mix in line 31 may have a gravity A.P.I. in the range 10-25 and a Conradson carbon residue in the range 1-10% and a viscosity in the range 200-600 SUS at 210 F., more or less. The deasphalted oil solvent mix is transferred from line 31 via line 32 through a vaporizing device, such as pressure reducing or expansion valve 34, and through a heater 35 into deasphalted oil ilash drum 36. "From ash drum 36 there is removed overhead via line 38 a iirst vapor phase containing deasphalting solvent vapor. There is also removed from the bottom of ash .drum 36 via line 39 a rstliquid phase containing deasphalted oil admixed with deasphalting solvent. The rst liquid phase Y.is passed via line 39 through a second vaporizing device, such as pressure reducing valve 40, whereby it is partially vaporized to a lower temperature and pressure than the temperature and pressure prevailing in line 38. The resulting partially vaporized irst lliquid phase is then passed in indirect countercurrent heat exchange relationship via ,lines 41a, 41b and 41e` by means of heat exchangers 42a, 42b and 42e `with -said first vapor phase vintroduced into vthe heat exchangers via lines 44a, 44b and 44C, respectively. After the above-described heat exchange has taken place the resulting partially vaporized rst liquid phase is recovered via line 45 and introduced into deasphalted oil ash drum 46. The resulting cooled rst vapor phase, approaching the temperature of the partially vaporized first liquid phase in lines 41a, 41b and 41C, is recovered via line 48 and, if necessary, after having been cooled in cooler 49 is introduced into deasphalting solvent storage tank 28 from which the resulting liquetied deasphalting solvent can be returned to deasphalting tower 26 via line 29.

The partially vaporized first liquid phase introduced into reasphalted oil ilashdrum 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 52 comprising substantially only deasphalted oil. The deasphalting solvent vapor phase in line 51 is cooled in cooler 54 and the resultingliquetied deasphalting solvent is passed via lines 55 and 56 into deasphalting solvent storage tank 58.

The liquid asphalt deasphalting solvent mix leaving deasphalting tower 26 is passed via line 30 through a heater 59 and line 60 into asphalt flasher 61. The resulting vaporized deasphalting solvent is removed overhead from asphalt asher 61 via line 62 for introduction into line 32 into admixture with the deasphalted oil mix therein to aid in the vaporization of deasphalting solvent therefrom and for the eventual liquefaction and recovery of the deasphalting solvent as indicated hereinabove. There is removed from asphalt asher 61 a liquid asphalt bottoms via line 64 which is introduced into asphalt stripper 65 for the removal overhead via line 66 of residual deasphalting solvent by the Vinjection of high temperature,

,high pressure steam into asphalt stripper 65 via line 68. The resulting steam stripped asphalt is removed as liquid bottoms from asphalt stripper 65 via line 69.

The resulting admixture of steam and vaporized deasphalting solvent removed from asphalt stripper 65 via line 66 is introduced into the upper portion of deasphalted oil stripper 7 0 wherein it is admixed with the deasphalted oil bottoms removed from deasphalted oil ash drum 46 via line 52. High pressure, high temperature steam is introduced into the lower portion of deasphalted oil stripper 70 via line 71 and there is removed Overhead from oil stripper V'/"0 via line 72 a vaporous admixture-of deasphalting solvent and steam. This vaporous admixture is cooled in cooler 74 to a temperature suiciently low to condense or liquefy substantially all of the deasphalting solvent and steam present in the admixture, e.g., cooled to a temperature about 100 F. and lower. The resulting cooled admixture is then introduced via line 75 into water separator 76 from which water condensate is removed via line 78 and the resulting condensed liquefied deasphalting solvent is removed via lines 79 and S6 into deasphalting solvent storage tank 58 for reuse in the deasphalting operation. If 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 deasphalting solvent storage tank 28.

Referring now to the gas oil fraction recovered from atmospheric flasher 15 via line 19, this .gas oil fraction is introduced into topping still 82 where there is produced overhead vialine 84 a 500 F. end point naphtha `fraction particularly suitable as a catalytic cracking charge stock. The bottoms fraction recovered from topping still 82 via line 85 is combined therein with the gas oil Afractions Aremoved from vacuum still 21 via lines 22, 24 'and 95.

The deasphalted oil recovered lfrom deasphalted oil stripper 70 via line 86 after cooling in cooler 88 is introduced via line 89 into pretreater `90 wherein itis 4cortvtacted with Va liquid selective solvent ,for aromatic hydrocarbons, such ,as furfural. ,Pretreater .90,may be any :suitable device vfor .effectingliquid-liquid .contact between vamante the liquid selective solvent employed and the deasphalted oil being pretreated. Preferably pretreater 90 is`an apparatusv suitable for effecting continuous countercurrent liquid-liquid contact, such as a packed tower, a centrifugal contactor or a rotating disc contactor. If desired, there 4may be blended or otherwise admixed with the deasphalted oil introduced via line 89 into pretreater 90 added deasphalting solvent introduced Via line 80 into admixture withthe'deasphalted oil in line 89. The deasphalted oil introduced via line 89 into pretreater 90 is contacted jtherein with a solvent extract mix comprising selective solvent, such as furfural, together with the dissolved hydrocarbons therein, Awhich 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 82 and the gas oil fractions removed from vacuum still 21 via lines 22, 24 and 95. If desired, liquid deasphalting solvent fromv deasphalting solvent storage tank 58 may be admixed via lines 80 and 96 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 26 via line 31 may be introduced Via line 95 into line 85 for eventual admixture with the pretreated deasphalted oil in selective solvent refining unit 91. Y

The resulting extract efiiuent from pretreater 90 is recovered via line98 and introduced into selective solvent recovery unit 99 wherein the selective solvent, e.g., furfural, is recovered and recycled to selective solvent refining unit 91 via line 100. The resulting separated extract is recovered from selective solvent refining unit 99 via line 101. Various selective solventsk may be employed inselective solvent refining unit 91, these include furfural, *phenols (Selecto), nitrobenzene, sulfur dioxide, ,di chloroethyl ether (Chlorex), dimethyl formamide and other selective solvents for aromatic hydrocarbons.

The resulting admixture in line 85 comprising the bottoms fraction from topping still 82, the gas oil fractions from vacuum still 21, selective solvent pretreated deasphalted oil from pretreater 90 and, if desired, the vliquid deasphalting solvent recovered from deasphalting solvent storage tank 58 via lines 80 and 96 or a portion ofthe deasphalted oil-deasphalting solvent mix recovered from deasphalting tower 26 via lines 31 and 95, is introduced into selective solvent refining unit 91 wherein it flows in liquid-liquid countercurrent contact with a liquid selective solvent, such as furfural, which selectively dissolves or extracts the more aromatic hydrocarbons therefrom. .As previously indicatedthe resulting extract mix from selective solvent refining unit 91 comprising selective solvent and extracted hydrocarbons is recovered via line 92 and introduced into pretreater 90.

' The aromatic type hydrocarbons contained in the extract mix introduced into pretreater 90 via line 92 and employed to contact and pretreat the deasphalted oil lintroduced-thereinto via line 89 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-conytaining components (the presence of which is undesirable lin 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 91 a greater overall degree of metals yremoval is possible. Also, the selective solvent contained in the deasphalted oil raffinate .recovered from pretreater 90 via line 94 serves to prefdilute .the deasphalted oil raffinate introduced in admix- -turewith the gas oils and bottoms fraction via line85 `into selective solvent refining unit 91. This' predilution Aits of the feed to the selective solvent refining unit 91 ncreases the efficiency of the selective s olvent refining operation therein. Still further, the deasphalted oil introduced into pretreater via line 89 removes from the extract mix introduced thereinto via line 92 the lower molecular weight, more parafinic -hydrocarbons therein which may have been taken into solution n the extract mix during the refining of the combined feed 'admixture supplied to the Selective solvent refining unit 91 via line 85. These more parafiinic materials are returned continuously to the selective solvent refining unit 91 and thus the overall yield of the rainate recovered from selective solvent refining unit 91 via line V102 isincreased. The contacting or'scrubbingof the extract'mix within pretreater 90 should result in a reduction in the quantity of the more parafiinic materials withdrawn from pretreater 90 as solvent efiiuent via line 98 and eventually removed from the system as extract suitable as cutter stock via line 101.

The raffinate removed from selective solvent refining unit 91 via line 102 having a reduced metals content, eg., 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 8 4 vwith the 500 F. end point naphtha fraction recovered from topping still 82 and introduced as feed stock to fluid catalytic cracking unit 104 where it is contacted with fluidized cracking catalyst.

A cracking catalyst usually comprises an oxide of metals of groups II, III, IV and V of the periodic table, for example, asilica-alumina catalyst Ycontaining about 530% by weight alumina. The average particle size lof the cracking catalyst particles is usually below about 200 microns, a size sufficient to produce a dense fiuidized bed of cracking catalyst.

The resulting cracked catalyst eluent from fluid catalyticcracking unit 104 is introduced via Vline 105 into fractionator 106 wherein it is fractionated into a catalytic cracked naphtha recovered via line 1,08, a catalytic cracked light gas oil recovered via line 109 and a relatively heavy cycle gas oil, e;g., FCCU decanted oil, re-

covered via line 110. v

T o the asphalt recovered from asphalt stripper 65 via line 69', which asphalt may have a ring and ball softening point in the range 18o-'325 F., is added at least a portion ofthe gas oil fractions recovered from catalytic cracking fractionator 106 via lines 109, 110 and 111 and at least a portion of the selective solvent-free extract recovered from selective solvent recoveryuzone 99 via line 101, the resulting stream of combined catalytic cracked gas oils and selective solvent extract being added via line 111 as cutter stock to the asphalt in line 69.

If desired, at least a portion of the catalytic cracked light gas oil recovered from fractionator 106 via line 109 and/or the heavygas oil vorA FCCU decanted oil recovered via line 110 are passed via lines 111 and 89 to pretreater 90 or in admixture .via lines 112 and 85 to selective solvent refining unit91 for the recovery of the more parafiinic constituents therefrom asV rafiinate via line 102 to provide additional catalytic cracking charge stock and for the eventual recovery of the more aromatic constituents therefrom as extract via line 1 01 as cutter stock. When the gas oil recovered from catalytic cracking fractionator 106, such as theFCCU decanted oil, possesses a relatively `high metals content, e.g., more than about 30 ppm. heavymetals, the -gasoils are preferably introduced via lines 111 and 89 as feed to pretreater 90 .in order to reduce its metals content.

some extent by the composition of feed thereto and the -type ofselective` solvent-employed thereim In vthurinstance where furfural is employed as the selective solvent pretreater 90 is operated at a solvent dosage in the range 75-250%, e.g., 125%, basis oil charge whereas selective solvent rening unit 91, employing the same solvent (furfural), might be operated at a relatively lower solvent dosage in the range 10-100%, e.g., about 25%, basis oil charge thereto. By operating in accordance with this feature of the invention the yield of recoverable catalytic cracked naphtha is further increased.

Cutback product asphaltis recovered vialine 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 11111. 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 asher from which was recovered overhead approximately 46% total volume yield of gas oil, naphtha and atmospheric viscosity broken gas oil, basis 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 asher 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 was recovered 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 original crude mixture or about 33.8% volume basis reduced crude. The vacuum still bottoms had a gravity of about 3.6 A.P.I., a penetration (100 gm./5 see/77 F. cm. 102) inthe range 27-29 and a Conradson carbon residue in the range 26-33.

Portions of the above-identified vacuum still bottoms were solvent deasphalted with liquid isobutane as the deasphalting solvent, employing a solventmil volume ratio of 5:1 at various temperatures in the range 20D-275 F. and at a pressure in the range ZOO-500 p.s.i.g. The re sults of these operations are set forth in accompanying Table No. I.

Table No. l

neaspnamng neaspha'nea ou Solvent Yield, Carbon Y Tenp., Press., Wt. 'Res- Ppm. Rpm. 'Ppm p.s.i.g. Percent due, Fe Ni V Percent Charge. 26 80 150 350 Isobutane.. 200 230 46. 0 5. 9 6 11 9 Do.. 235 335 10. 1 ,5. 0 6 8 5 Do....- 245 385 42.0 4.1 Do..... 220 475v v35. 6 ,3. 0 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 a pressure of about 390 p.s.i.g.; there was also directly recovered a liquid deasphalting solventasphalt mix containing asphalt and liquid isobutane at about the same aforesaid temperature and pressure. The liquid deasphalted oil-isobutane mix leaving the deasphalting operation at a pressure of about 390 p.s.i.g. was partially vaporized by passage through an expansionvalve and admixed with the hot vapors (isobutane and cutter stock) from the asphalt asher or separator to yield a rst vapor phase at a temperature of about 190 F. and at a pressure of 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. The first liquid phase is then partially vaporized by passage through an expansion valve to yield a partially liquefied admixture containing deasphalted oil (together with the previously admixed cutter stock) and vaporous isobutane at a temperature of about 145 F. and at a pressure of at least about 75 p.s.i.g., preferably about 100 p.s.i.g. The resulting vaporous admixture is then passed in indirect heat exchange relationship with said rst vapor phase at a temperature in the range l200 F. (at a pressure about 205 p.s.i.g.) whereby the isobutane deasphalting solvent in said first vapor phase is condensed and liquefied or is readily condensed and liquelied by supplemental cooling to a temperature of about 190 F. the pressure in the resulting cooled lirst vapor phase being at least about 160 p.s.i.g. and higher if necessary in order to elect liquefaction of the isobutane deasphalting solvent. The resulting admixture of liquid deasphalted oil and vaporous isobutane derived from first said liquid phase, after having been passed in indirect heat exchange relationship with said first 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 p.s.i.g., vaporous isobutane which is liquefied and condensed by cooling to a temperature of about 126 F. at a pressure of at least about 95 p.s.i.g. The separated deasphalted oil is then steam stripped to effect substantially complete removal of isobutane there from and the resulting steam stripped isobutane is recovered by cooling the euent resulting from the steam stripping operation to 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.g. and at least sulcient 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 l5.3-l6.8 A.P.I., a viscosity SUS 210 F. in the range 238-281 and a K factor of about 11.7.

The liquid asphalt deasphalting solvent mix phase containing asphalt admixed with isobutane, after the addition of an amount of cycle gas oil or cutter stock such as deasphalted oil, is passed to the asphalt heater and heated to a temperature 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 admixture of isobutane and cutter stock which lis admixed with vaporous isobutane from the deasphalted oil ash drum, from which resulting 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 100 p.s.i.g., and the admixed cutter stock separated with the deasphalted oil. The liquid asphalt bottoms recovered from the asphalt separator is then steam stripped for the removal of any residual isobutane and recovered as procluct. There was recovered from the aforementioned operations an asphalt having la ring and ball softening point in the range ZOO-300 F.

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 10D-200% volume, eg., 125%, basis oil charge, the furfural solvent extract mix having been derived from the furfural solvent refining of the resulting deasphalted oil raiiinate Lin admixture with VPS gas oil, said subsequent furfural reiining being carried out at a solvent dosage in the range 15-75%, basis oil charge.- The rainate resulting fnom the subsequent furfural refining operation possesses a significantly lower metals content, substantially below 30 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 refining 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 10-200% 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 raiinate (selective solvent refined deasphalted oil) is further reduced, e.g., below about p.p.m.

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:

1. A method of treating an asphaltic oil which comderdeasphalting conditions of temperature and pressure to eiect separation of asphaltic constituents Afrom saidVV oil, recovering from the aforesaid operation a deasphalted oil mix comprising oil having a reduced amountV of asphaltic constituents and containing a portion of said deasphalting solvent and a liquid asphalt mix containing asphalt admixed with 'another portion of said deasphalting solvent, admixing a relatively high boiling liquid petroleum fraction with said asphalt mix, heating the resulting admixture, treating the resulting heated admixture to yield a vapor phase comprising substantially al1 'of thel deasphalting solvent and petroleum fraction in said admxture and introducing said vapor phase into said deasphaltecl oil mix.

2. A method in accordance with claim 1 wherein said deasphalting solvent is isobutane.

3. A method in accordance with claim 1 wherein said petroleum fraction is substantially the same as said de- Y asphalted oil.

4. A method in accordance with claim 1 wherein said petroleum fraction has a boiling point range in the range 30D-825 F.

5. A method in accordance with claim 1 wherein said petroleum fraction is derived from the aforesaid deasphal-ted oil.'

References Cited in the tile ofthis patent UNITED STATES PATENTS 2,110,905 Chase Mar. 15,1938 2,192,253 Adams Mar, 5, v19 40

Claims (1)

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 CONSTITUENTS FROM SAID OIL, RECOVERING FROM THE AFORESAID OPERATION A DEASPHALTED OIL MIX COMPRISING OIL HAVING A REDUCED AMOUNT OF ASPHALTIC CONSTITUENTS AND CONTAINING A PORTION OF SAID DEASPHALTING SOLVENT AND A LIQUID ASPHALT MIX CONTAINING ASPHALT ADMIXED WITH ANOTHER PORTION OF SAID DEASPHALTING SOLVENT, ADMIXING A RELATIVELY HIGH BOILING LIQUID PETROLEUM FRACTION WITH SAID ASPHALT MIX, HEATING THE RESULTING ADMIXTURE, TREATING THE RESULTING HEATED ADMIXTURE TO YIELD A VAPOR PHASE COMPRISING SUBSTANTIALLY ALL OF THE DEASPHALTING SOLVENT AND PETROLEUM FRACTION IN SAID ADMIXTURE AND INTRODUCING SAID VAPOR PHASE INTO SAID DEASPHALTED OIL MIX.

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