US2895908A - Furfural solvent refining and recovery process - Google Patents

Description

.Ily 2l, 1959 D. K. BEAVONA FURFURAL SOLVENT REFINNG AND RECOVRY PROCESS Filed March 29, 1957 United States arent FURFURAL SOLVENT REFINING AND RECOVERY PROCESS David K. Beavon, Darien, Conn., assigner to Texaco, Inc., a corporation of Delaware Application March 29, 1957, Serial No. 649,47 6 9 Claims. (Cl. 208-327) This invention relates to solvent refining. More particularly, this invention relates to a solvent refining process employing liquid furfural as the selective solvent. Still more particularly, this invention relates to a method of operating a furfural solvent refining process whereby the turfural recovered from the resulting raffinate and extract phases contains a reduced amount of light oils, such as co-boiling aromatic hydrocarbons in the range 30G-500 F. and/or a reduced amount of water.

The practice of this invention is particularly applicable to the solvent refining of gas oils, such as virgin gas oils, pipe still gas oils, catalytic cycle gas oils, light and/or heavy gas oils and the like. In one embodiment the practice of this invention is particularly applicable to the solvent refining of petroleum oils, particularly petroleum oils which contain hydrocarbons having a boiling point in the range 30G-500 F., more or less, and which are preferentially soluble in furfural. It has been observed that in a furfural solvent refining operation there tends to be a buildup of these light aromatic hydrocarbon oils (boiling point in the range SOO-500 F.) in the furfural employed as the selective solvent. These light oils tend to dilute the furfural, lessen its capacity and at the same time decrease the gravity differential between the furfural (extract phase) and the refined oil (raffinate phase) thereby making separation between the raffinate phase and the extract phase more difficult.

Accordingly it is an object of this invention to provide an improved method for carrying out a furfural refining operation.

It is another object of this invention to provide an improved method for the recovery of furfural employed in a solvent refining operation.

Still another object of this invention is to provide in a solvent refining operation an improved method for the recovery of furfural from the raliinate and extract phases.

Yet another object of this invention is to provide a method in a solvent refining operation for the recovery of liquid furfural having a relatively reduced amount or concentration (less than equilibrium) of substantially coboiling light oils (boiling point inthe range SOO-500 F.) and/ or Water dissolved therein.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure and drawing wherein there is schematically illustrated a furfural solvent refining process carried out in accordance with the teachings of this invention.

Referring now in detail to the drawing a solvent relining tower 11, which may be a packed tower, a bubble tray tower for liquid-liquid contacting, combination of mixers and settlers, a rotating disc contactor or a centrifugal contacter or any combination of these, is supplied at one end via line 12 with liquid furfural and at the other end via line 14 with a suitable hydrocarbon oil, such as a gas oil, to be solvent rened. There is removed overhead from the solvent refining or treating tower 11 via line 15 a raffinate phase which is passed through heat exchanger 16 and line 18 into rafiinate stripper 19 wherein it is contacted with steam introduced thereinto via line 20. There is `recovered overhead from raffinate y 2,895,908 Patented July 2l, 1959 ICC stripper 19 via line 21 a vaporous admixture of furfural, oil and water, such as an azeotrope containing these materials, which is passed to condenser 22 wherein it 'is condensed and the resulting condensate passed via line 24 into settling zone 25. Settling zone or settler 25 is provided with compartments or suitable baffles therein to effect a separation between the resulting condensed oil, water and furfural, the furfural being most dense settling as the bottom phase, the water being of intermediate density settling as the intermediate phase and the oil having the lightest density being the top phase. There is recovered from the bottom of rafiinate stripper 19 via line 26 solvent refined oil as product.

The extract phase comprised predominantly of furfural and more aromatic hydrocarbons preferentially dissolved therein is recovered from solvent refining zone 11 via conduit 28 and passed through heater 29 and line 30 into a rst vacuum flasher 31. There is recovered overhead from vacuum flasher 31 via line 32 a vaporous admixture of furfural and steam substantially free of oil. The liquid bottoms in vacuum flasher 31 is recovered via line 34 and passed through heater 35 and line 36 into a second vacuum flasher 38. There is recovered overhead from vacuum flasher 38 via line 39 a vaporous admixture of furfural and oil and co-boiling with furfural, and substantially no water.

The overhead vaporous admixture from vacuum flasher 31 is condensed in condenser 4t) and passed via line 41 into settler 42 wherein liquid furfural settles from the Water. The water is removed from settler 42 via line 44. The liquid furfural, containing a certain amount of water dissolved therein but substantially free of oil, is removed from settler 42 via line 45.

The overhead vaporous admixture from vacuum flasher 38 in line 39 is condensed in condenser 46 to yield liquid furfural and oil substantially free of water. The mixture of liquid furfural and oil from condenser 46 is removed via line 48.

The liquid bottoms from vacuum flasher 38 is removed via line 49 and passed through heat exchanger 50 and introduced via line 51 into extract stripper 52 wherein furfural is fractionally distilled by the introduction of steam via line 54 into the lower portion of stripper 52. There is recovered overhead from stripper 52 via line 55 a vaporous admixture of furfural, oil and water, such as a furfural-oil-Water azeotrope, which is condensed in Condenser 56 and passed via line 58 into settler 25. Settler 25 is provided to effect a separation between the oil and Water and furfural therein. Settler 25, as previously mentioned, is also employed as a settling zone for the overhead admixture from rafiinate stripper 19. There isy recovered from settler 25 via line 59 furfural substantially saturated (equilibrium amount) with water at the temperature at which settler 25 is operated. This furfural also contains dissolved therein an equilibrium amount of oil. The furfural in line 59 is combined with the furfural in lines 45 and 48 by means of line 60 and passed to furfural supply tank 6l. From supply tank 61 furfural is returned to the solvent rening zone 11 via lines 62 and 12. From time to time, as needed, additional fresh furfural is supplied to the solvent refining zone 11 from an outside source, not indicated.

In the foregoing described operations, as previously indicated, the practice of this invention is practcularly applicable to the solvent refining of gas oils, particularly gas oils containing aromatic hydrocarbons or those hydrocarbons having a boiling point in the range SOO-500 F. and preferentially soluble in furfural.

The vacuum iiashers 31 and 38 may be operatedy at any suitable conditions to effect the desired separation. For example, both flashers may be operated at a suitable absolute pressure in the range 5-700 mm. Hg. It

may be desirable to operate asher 31 at an absolute pressure greater than the absolute pressure in flasher 38 although suitable results are also obtainable when the absolute pressure in iiasher 38 is the same as or greater than the absolute pressure in asher 31. Generally, the higher the absolute pressure the higher the temperature required to effect flashing. Accordingly, it is desirable to operate these ashers in the lower absolute pressure range, such as at a pressure in the range -200 mm. Hg, flasher 31 being operated at an absolute pressure in the range 50-500 mm. Hg and flasher 38 at a lower pressure in the range 10-200 mm. Hg.

In the practice of this invention settling zones 25 and 42 and condenser 46 are operated at a suitable convenient temperature, even, if desired, at substantially the same temperature. A temperature in the range 50- 170 P. is usually adequate.

The solvent reiining zone, indicated as treating tower 11 in the drawing, is operated under suitable conditions of temperature and pressure and solvent charge oil ratios to effect the desired separation and to maintain the resulting raffinate and extract phases immiscible with respect to each other.

By operating a solvent refining process in the manner set forth hereinabove with reference to the drawing it is seen that the resulting combined liquid furfural supplied via line 60 to furfural supply tank 61 for use in the solvent refining operation contains less than the equilibrium amount of water and/ or oil dissolved therein. This is brought about by virtue of the fact that the furfural recovered overhead from vacuum iiasher 38 via line 39 is substantially free of water and by virtue of the fact that the furfural recovered overhead from vacuum asher 31 via line '32 is substantially free of oil. The furfural recovered overhead vial line 32 contains substantially all of the water present in the extract phase removed from treating tower 11 via line 28 and is separately recovered and discharded via line 44. Water is sometimes employed admixed with the furfural in treating tower 11 to increase or improve the selectivity of the selective solvent (furfural) for the more aromatic hydrocarbons in the charge oil. That amount of furfural recovered as liquid bottoms from vacuum flasher 38 via line 49 is also recovered overhead from extract stripper 52 via line 55 and eventually from settling zone 25 via line 59. The furfural in line 59 contains equilibrium amounts of water and oil dissolved therein depending upon the temperature conditions at which settler 25 is operated. However, the furfural contained in line 59 when admixed with the furfural recovered via lines 45 and 48 contains less than equilibrium amounts of oil and water, respectively. As a result of combining the furfural streams flowing in lines 59, 45 and 48 there is supplied to furfural supply tank 61 via line 60 a furfural stream having less than an equilibrium amount of oil and water, respectively.

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

I claim:

1. In an operation wherein furfural is employed as the selective solvent for the solvent refining of a hydrocarbon oil to yield a furfural rich phase containing furfural and more aromatic hydrocarbons dissolved therein the improvement which comprises flashing said furfural rich phase at a subatmospheric pressure to yield overhead a rst vapor stream substantially free of oil and comprising furfural and water and a first liquid bottoms phase, subjecting said first liquid bottoms phase to ashing at a subatmospheric pressure to yield overhead a second vapor stream substantially free of water and comprising furfural and oil and a second liquid bottoms phase comprising substantially only furfural and oil, condensing said first vapor stream to separate liquid furfural therefrom, condensing said secondvapor stream, subjecting 4 said second bottoms phase to distillation in the presence of steam to separate overhead therefrom a vaporous admixture of oil, steam and substantially all of the furfural in said second bottoms phase, condensing the resulting overhead vaporous admixture to separate furfural therefrom, combining the furfural separated from said condensed rst vapor stream, the condensed second vapor stream and the furfural separated from said condensed vaporous admixture and employing the resulting combined furfural as selective solvent in the aforesaid solvent refining of said hydrocarbon oil.

2. A process in accordance with claim 1 wherein said subatmospheric pressure is in the range 5-700 mm. Hg absolute.

3. A process in accordance with claim 1 wherein said hydrocarbon oil contains hydrocarbons preferentially soluble in furfural and having a boiling point in the range 30G-500 F.

4. A process for solvent refining a hydrocarbon oil which comprises contacting said oil with liquid furfural to form a ratfinate phase and a furfural-rich extract phase, subjecting said rainate phase to fractional distillation in the presence of steam to remove overhead a first vaporous admiXture comprising furfural, oil and steam, and to yield a rst liquid bottoms comprising substantially only solvent refined oil, dashing said extract phase at a subatmospheric pressure to yield overhead a first vapor stream substantially free of oil and comprising furfural and water and a second liquid bottoms phase, subjecting said second liquid bottoms phase to flashing at a subatmospheric pressure to yield overhead a second vapor stream substantially free of water and comprising furfural and oil and a third liquid bottoms phase comprising substantially only furfural and oil, condensing said irst vapor stream to separate liquid furfural therefrom, condensing said second vapor stream, subjecting said third bottoms phase to distillation in the presence of steam to separate overhead therefrom a second vaporous admixture of oil, steam and substantially all of the furfural in said third bottoms phase, condensing said rst and second overhead vaporous -admixtures to separate furfural therefrom, combining the furfural condensed and separated from said first and second vapor streams with the-furfural condensed and separated from said first aud second vaporous admixtures and employing the resulting combined furfural as selective solvent in the aforesaid solvent refining of said hydrocarbon oil.

5. A process in accordance with claim 4 wherein said subatmospheric pressure is in the range 5-700 mm. Hg absolute.

6. A process in accordance with claim 4 wherein said hydrocarbon oil is a gas oil.

7. A process in accordance with claim 4 wherein said vaporous admixtures and said vapor streams are condensed and the resulting liquid furfural separated at a temperature in the range 50-170 F.

8. A process in accordance with claim 4 wherein said hydrocarbon oil contains hydrocarbons preferentially soluble in furfural and having a boiling point in the range 30D-500 F.

9. A process in accordance with claim 4 wherein said rst and second vaporous admixtures are condensed and the resulting liquid furfural separated from a common settling zone.

References Cited inthe leof this patent UNITED STATES PATENTS 2,186,298 Kiersted et al. Jan. 9, 1940 2,526,722 Beavon Oct. 24, 1950 2,613,174 Ockert Oct. 7, 1952 2,685,556 Hachmuth Aug. 3, 1954 2,742,400 Gross Apr. 17, 1956 2,745,790 Manley May l5, 1956 2,809,222 Hawkins Oct. 8, 19,57

Claims (1)

1. IN AN OPERATION WHEREIN FURFURAL IS EMPLOYED AS THE SELECTIVE SOLVENT FOR THE SOLVENT REFINING OF A HYDROCARBON OIL TO YIELD A FURFURAL RLICH PHASE CONTAINING FURFURAL AND MORE AROMATIC HYDROCARBONS DISSOLVED THEREIN THE IMPROVEMENT WHICH COMPRISES FLASHING SAID FURFURAL RICH PHASE AT A SUBATMOSPHERIC PRESSURE TO YIELD OVER HEAD A FIRST VAPOR STREAM SUBSTANTIALLY FREE OF OIL AND COMPRISING FURFURAL AND WATER AND A FIRST LIQUID BOTTOMS PHASE, SUBJECTING SAID FIRST LIQUID BOTTOMS PHASE TO FLASHING AT A SUBATMOSPHERIC PRESSURE TO YIELD OVERHEAD A SECOND VAPOR STREAM SUBSTANTIALLY FREE OF WATER AND COMPRISING FURFURAL AND OIL AND A SECOND LIQUID BOTTOMS PHASE COMPRISING SUBSTANTIALLY ONLY FURFURAL AND OIL, CONDENSING SAID FIRST VAPOR STREAM, TO SEPARATE LIQUID FURFURAL THEREFROM, CONDENSING SAID SECOND VAPOR STREAM, SUBJECTINGG SAID SECOND BOTTOMS PHASE TO DISTILATION IN THE PRESENCE OF STEAM TO SEPARATE OVERHEAD THEREFROM A VAPOROUS ADMIXTURE OF OIL, STEAM AND SUBSTANTIALLY ALL OF THE FURFURAL IN SAID SECOND BOTTOMS PHASE, CONDENSING THE RESULTING OVERHEAD VAPOROUS ADMIXTURE TO SEPARATE FURFURAL THEREFROM, COMBINING THE FURFURAL SEPARATED FROM SAID CONDENSED FIRST VAPOR STREAM, THE CONDENSED SECOND VAPOR STREAM AND THE FURFURAL SEPARATED FROM SAID CONDENSED VAPOROUS ADMIXTURE AND EMPOLYING THE RESULTING COMBINED FURFURAL AS SELECTIVE SOLVENT IN THE AFORESAID SOLVENT REFINING OF SAID HYDROCARBON OIL.

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