US 3310484 A
Description (OCR text may contain errors)
United States Patent Cfiice 3,310,484 Patented Mar. 21, 1967 3,310,484 1 THERMAL CRACKING IN AN OXYGEN FREE ATMOSPHERE Ralph Burgess Mason, Denham Springs, and Glen Porter Hamner, Baton Rouge, La., assignors t Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Filed May 20, 1965, Ser. No. 457,466 10 Claims. (Cl. 208125) This invention is directed to the conversion of crude residua, asphaltenes, aromatic tars, and the like usually having initial boiling points of about 650 F.+ to low sulfur, low metals, lower boiling 430 F.+ gas oil hydrocarbons by the noncatalytic liquid-phase thermal depolymerization of such residua in the presence of an organic solvent (boiling range 150 to 800 F.) at temperatures of about 650 to 900 F. substantially in the absence of available (molecular) oxygen for residence times of 0.5 to 6.0 hours.
More particularly, the present invention is concerned with the upgrading of petroleum oils, particularly heavy high boiling oils such as vacuum residua, to prepare theregas oil having a boiling range of about 430 F.+ (usually 430 F. to 1100" F.) by liquid phase, thermal, noncatalytic, nonhydrogen donor diluent cracking of the feed 'in the presence of a monocyclic, bicyclic, or tricyclic aromatic solvent and essentially in the absence of oxygen, viz. 0.1 wt. percent oxygen to reduce the molecular weight thereof and obtain higher value, more useful gas oils of low metals and low sulfur content per gallon and eminently suited as feedstock to catalytic cracking and hydrocracking operations.
The present invention in its essential features comprises the following steps. First, the virgin residua feed is blended at temperatures of 200 to 450 F. with a solvent (preferably an aromatic solvent having a boiling point range of about 400 to about 600 F.) in the absence of oxygen. Then the blend of feed residua plus solvent is heated at a temperature of about 650 to 900 F. for from 0.5 to 6.0 hours and usually 0.5 to 4 hours. This time period is the average residence time for which the residua feed is subjected to these temperatures in the presence of the solvent. Then the heat-soaked blend is filtered using any conventional filtration system to remove metals, sulfur, carbonaceous solid materials, etc. Following the filtration step, the filtered blend (solution) is fractionally distilled to obtain a small amount of naphthas and gasoline fractions as a top stream; a side stream composed of the initial solvent; and a bottom stream (main product) composed of the lower molecular weight hydrocarbon gas oils having a usual boiling point range of 430 to 1000 F. with a significantly reduced sulfur and metals content.
An important process feature of this invention is that the blend of feed and solvent should not be heated at the above temperatures, 650 to 900 F. in the absence of the solvent for longer than 30 minutes and preferably no longer than 10 minutes at these temperatures during the fractional distillation and/or processing steps. In other words, the blend of solvent and converted feed during the distillation step should be heated for no more than 30 minutes as the solvent is being separated from the converted product. Failure to observe this process feature will result in coke formation and reversal of the depolymerization process.
In accordance with this invention, various high molecular weight sulfur containing and metal containing virgin residua feeds, which can be the bottoms from crude oil distillation and/or conversion processes, can be employed as feeds for the instant process. Exemplary feedstock materials to the present process can be: atmospheric residua and vacuum residua; asphaltenes; aromatic tars; coal tars; shale oils; heavy synthetic oils; natural tars and asphalts; aromatic extracts; cycle stocks; pitches; and the like. These materials can be liquids or solids at room temperature and usually possess API gravities of -8 to +30, molecular weights of 200 to 20,000 and initial boiling points above 650 F. Particularly preferred feedstocks, which can be employed in accordance with this invention, are heavy residua characterized by API gravities of 0 to 20, molecular Weights of 400 to 6000 and initial boiling points above about 950 F.
In accomplishing the process of this invention, the sulfur-containing metals-containing, high molecular weight feedstock is blended usually with an aromatic solvent in a volume ratio of about 0.5:1 to 5:1 (volumes of aromatic solvent per volume of residue feedstock). During the blending step the solvent can be, and preferably is, heated to 200 to 450 F., preferably about 200 to 300 F., and the system is blanketed with an inert gas, for example, nitrogen, hydrogen, etc. The available (molecular) oxygen content of the feedstock and solvent should be less than 0.1 wt. percent, and preferably the feedstock and solvent should contain less than p.p.m. oxygen from the onset until the completion of thermal depolymerization. The blending of the feedstocks in the solvent is accomplished substantially in the absence of both available oxygen (molecular), oxygen and oxygen containing compounds which thermally release molecular oxygen in situ during the heat treatment to form intimate blend of feedstock and solvent.
The blended solution of feed and aromatic solvent(s) is then heated in the liquid phase essentially in the absence of oxygen at temperatures ranging from 650 F. to 900 F., usually at temperatures ranging from 650 F. to about 850 F., and more preferably at temperatures ranging from about 675 F. to 775 F. The heating is continued to allow an average residence time for which the residual feed-solvent solution is subjected to these temperatures in the presence of the solvent for time periods of 0.1 to 6 hours, usually 0.5 to 6 hours, and more preferably from about 1 to 4 hours. During the thermal depolymerization (heating) step, pressures ranging from atmospheric pressure to about 2000 p.s.i.g. can be used. Usually, however,,the pressures employed range from about 20 p.s.i.g. to 2000 p.s.i.g., and preferably from about 200 p.s.i.g. to 1600 p.s.i.g. with hydrogen being employed to establish all or part of the pressure At the higher temperatures the pressure is adjusted upwards to insure the presence of the solvent in the liquid phase during thermal depolymerization.
Subsequent to the thermal cracking step, the solution containing the lower molecular weight gas oil product and solvent is filtered using any conventional filtration system, e.g. filters, centrifuge, settling tanks, etc. .useful to separate solid residues, such as metals, sulfur, carbonaceous residues, etc., from the liquid portion of the productcontaining, solvent-containing stream. These metals, sulfur containing compounds, and carbonaceous solid materials removed by the above filtration step usually represent less than about 20% by Weight solids based on the original residua feed. The solids, removed by filtration or centrifugation from the product containing stream prior to fractional distillation, can be processed for recovery of nickel, vanadium, sulfur compounds, and other metals present therein.-
An alternate process procedure to aid in the complete removal of the metals and sulfur compounds consists in a primary separation of the l000 F.+ unreacted product by either parafiinic solvent (C hydrocarbons) precipitation or vacuum flashing and by resolution of the 100 F.+ material in the recycle aromatic solvent either on the filter or in a mixing zone after the primary separation.
Subsequent to the filtration and/or primary separation step, the product containing stream is fractionally distilled to separate the starting solvent and the lighter overhead products including varying amounts of gasoline from the dernetallized, desulfurized 430 F. to 1000 F. gas oil product.
The present invention is capable of attaining conversions from the lower value, high Conradson carbon residua feedstock to the higher value desulfurized, demetallized gas oils with yields as high as about 70 to 80%. This constitutes a significant improvement over the more complicated and expensive catalytic or hydrogen donor diluent cracking procedures. Thus, the present invention requires neither use of a catalyst, nor the regeneration and/or replenishment of a hydrogen donating solvent; and the benefits and advantages of the improved process of this invention require neither a catalyst nor replacement of hydrogen to the aromatic solvent.
Moreover, the demetallization secured by the present process is excellent. Thus, when the feed contains 150 or more p.p.m. metals, the metals content in the product stream usually is below 20 p.p.m.
Another outstanding feature of the present invention, as compared to a coking procedure, is a reduction in the sulfur content of the gas oil fraction. Thus, sulfur content reductions of from 2.4 wt. percent in the residuum feed to the process to from 1.0 to 1.5 wt. percent in the gas oil product stream can be readily achieved in accordance with this invention.
A wide variety of solvents can be employed in accordance with the present invention. Preferably, however, the solvents employed are aromatic and more preferably naphthenic in nature. Usually the boiling point range of the solvents employed in accordance with this invention lies within the range of about 150 F. to 800 F. Thus, such solvents as benzene; toluene; ortho-, meta-, and para-xylene; ethyl benzene, etc. can be used. Preferably, however, the solvents used in this invention have a boiling point range from about 400 to about 600 F., and preferably are the highly boiling monocyclic, bicyclic and tricyclic hydrocarbon aromatic solvents. Exemplary materials suitable for use in accordance with this invention include, but are not limited to, the following: naphthalene, alkyl substituted naphthalenes, such as methyl naphthalene, anthracenes, phenanthrene, tetralin, decalin, phenol, xylidine, toluidine, phenylene diamine, amino phenol, a-methyl naphthyl amine, a-naphthol, ,B-naphthol, and materials of a similar nature which can have a variety of substitutents, said substituents being inert to the thermal cracking reactions involved to the extent that they do not interfere therewith. Mixtures of any two or more of the above solvents can be used.
According to a preferred embodiment of this invention following the fractional distillation step, the product stream bottoms, if not previously removed and taken in solution after the primary separation step, can be filtered to remove carbonaceous residue which can then be recycled back to the initial solvent dissolving step for further conversion of these higher molecular weight materials not converted on the initial pass through the process. With the abovementioned suitable solvents, thermal depolymerization occurs with very little coke formation. One special advantage of this preferred embodiment of the present invention resides in the fact that it enables the metal components to be segregated (concentrated) in the filtered solids thus rendering more amenable the economic recovery of the metals and of the other materials sought to be recovered from the insolubles. This is particularly true with respect to nickel and vanadium. For example, the conversion of asphaltenes from Bachaquero crude to naphthas and gas oil with low coke production can be readily accomplished in accordance with this invention. The coke yields in successive operations were, e.g., 11% and 8% based on the asphaltene portion of the charge when thermal depolymerization was conducted at temperatures of 700 to 810 F. for l to 4 hours residence time on heat, using methyl naphthalene and tetralin as the solvents, and controlling the oxygen content during the processing at less than p.p.m. Analyses of the insoluble residues removed by filtration and/or settling showed a high concentration of metals. The solid residues (insolubles) obtained by filtration and settling contained from 2.8 to 4.4 wt. percent vanadium. The Bachaquero crude from which these insolubles were obtained originally contained 2000 p.p.m. vanadium. The product gas oils (650 F. produced in the main product stream had only 1 to 16 p.p.m. of vanadium and 0 to 4 p.p.m. nickel. This serves to further indicate the economically attractive nature of this invention.
Multiple staging of the thermal cracking step can be conducted in order to minimize any problems encountered during thermal depolymerization due to different rates of depolymerization of various feed and/or various components in the same feed. Different rates of depolymerization can cause some depolymerized products to be subjected to temperature conditions too high and for much longer than is ideally desirable. To counteract this, the thermal depolymerization can be conducted by use of two or more depolymerization stages in the same pro-cessing scheme, each operating at a different temperature and residence time for depolymerization. Thus, the readily depolymerizable materials are removed at relatively mild conditions and the more refractory materials removed at more severe conditions in absence of the products in the milder operation. In addition to varying the severity of temperature and time during the thermal depolymerization over the plurality of thermal depolymerization zones in the same depolymerization step, it is also possible to operate the various depolymerization zones using different aromatic solvents or mixtures of aromatic solvents; but in order to minimize the amount of recovery equipment necessary, use of the same solvent throughout the thermal depolymerization step is a preferred procedure.
The present invention will be illustrated in greater detail by the following illustrative examples.
Example 1 A charge of 300 grams of asphaltenes obtained from Bachaquero feed was dissolved in 300 grams of methyl naphthalene. This charge was found to contain no naphtha products boiling below 430 F. and no gas oil products boiling in the range of 4844000 F. Of the 600 grams of total blended charge (blending being conducted at temperature of 300 to 400 F. for 10 minutes), 497.2 grams was used in thermal depolymerization (heat soaking) experiments. Some coke was formed, which was washed with'methyl naphthalene, and the solvent was used in subsequent heat treatments. These heat treatments consisted of heating in an autoclave to about 810 to 820 F. for about 30 minutes, and then heating at 700 to 750 F. for about 3 hours. Oxygen was excluded from the system, and an oxygen-free blanket of hydrogen gas was employed to insure an oxygen-inert atmosphere. Maximum pressure in these runs was about 1200 p.s.i.g. Prior to the heat treatment, the autoclave was pressure tested with hydrogen at about 200 p.s.i.g. which was vented to atmospheric pressure at the start of the heating. Thus the heat soaking was conducted in the 5. presence of hydrogen at one atmosphere pressure. The heat soaking charges were as follows:
The coke-metal-sulfur insoluble product was removed from the main product by filtration using a Soxhlet thimble filter, and the combined coke product from Runs A, B, C, and D was extracted with benzene in a Soxhlet extractor to remove the residual product and methyl naphthalene. Benzene was removed by air drying on the filter. The combined products were distilled to remove the 430 F. and below products, and the bottoms were further distilled to demonstrate the presence of material other than methyl naphthalene. Of a still charge of 413 grams, 396 grams was higher boiling than 430 F. This material had the following distillation characteristics:
Volume, percent: Temperature, F. 451
478 492 492 730 841 901 925 Recov., percent 95 Res. 2
The methyl naphthalene employed was distilled in the range of 457 to 485 F. Hence, appreciable low boiling material resulted from the asp-haltenes. These results, based on asphaltenes, are summarized in the table below in comparison with other results obtained wherein no solvent was employed.
Solvent Methyl None Naphahalene Wt. Percent Gas 1.7 10-11 Wt. Percent IBP430 F. Naphtha-.. 8. 2 10-15 Wt. Percent 430-925 F. Gas Oil 70.0 15-20 Wt. Percent Residue (Coke) 20.1 50-55 The above exemplary procedure illustrates the advantages of thermally depolymerizing higher molecular weight residua in the presence of a solvent with the exclusion of oxygen to convert the higher boiling materials to more valuable lower boiling gas oils.
Example 2 A 650 F.+ residua crude fraction (Bachaquero crude) was mixed at 150 F. with a 1:1 volume ratio of parafiinic C to C naphtha (naphtha to crude) while excluding oxygen, and allowed to settle for 0.5 to 6 hours. The insoluble residue was then filtered, and used as feed for the thermal depolymerization below. This feed material is solid at F. and nonvolatile at vacuum distillation conditions corresponding to a nominal boiling point of 1000 F.+.
The conversion of these high molecular weight asphaltenes from Bachaquero crude obtained by naphtha solvent precipitation of virgin feed to useful oil products with less coke formation than encountered in conventional thermal treatment is demonstrated in a set of runs which also show the necessity of precluding contact with air. An added feature is the maintenance of low temperatures when the high boiling component (asphaltenes) is in absence of the solvent. In this series of operations a charge consisting of 300 grams of asphaltenes from Bachaquero crude and 300 grams of methyl naphthalene, together with 25 cc. of ammonium hydroxide as a polymerization inhibitor were charged to a one-liter stirred autoclave and were heated for 3 hours at autogenic (autogenous) pressure.
The product was dis-charged and recycle material was obtained by pentane precipitation, filtration, solvent extraction of the precipitate (leaving nonsoluble residue on the filter), and recovery of the solvent.
In the first two cycles benzene was employed as the extractant, and prior to the extraction the precipitated, unreacted asphaltencs were air dried. Upon use of recycle methyl naphthalene, which was freed of peroxides by the recovery, the losses as insoluble residue were greatly reduced. This is shown by the following data.
'lIHE RMAL DEPOLYMERIZATION OF ASPHALTENES FROM BACHAQUERO CRUDE [750 F., 3 hrs. on heat, 25 cc. NH4QH solution in each cycle] Cycle 1 2 3 4 5 Charge, Grams:
Asphaltenes 300 167. 5 100 150 150 Methyl Naphthalene 300 800. 5 300 1 240 2 450 Recycle Produ 132. 5 200 220 Method of Recovery irom Precipitated Autoclave Prod Methyl Naphthalene Ext.
Soxhlet Solution Reflux Recovered Products, Grams:
IBP-430 Naplitha 29. 5 15. 2 18. 8 22 14. 5 480+ Gas Oil 124 89 91 Residue 81 104 16 11. 9 Wt. Percent Residue on Asphaltene Change.-- 27 39 11 s 1 Methyl naphthalene recovered in Cycle 3. 1 About 250 grams recycle methyl naphthalene and 200 grams recycle product.
monstrated by the recovery from cycles 9-1l.
In the same series of operations attempts to extract the recycle product from the pentane precipitate with methyl naphthalene were unsuccessful until air was excluded and the extraction was conducted under a hydrogen blanket. This is shown by the following data.
THERMAL DEPOLYMERIZATION OF ASPHALTENES FROM lO/lt d of original asphaltenes 39.9 grains were found as unreacted, 124 grams as 450 F.+ gas oil and 2.6 grams as residue. Conversion of some of the solvent to the gas oil fraction is indicated. These results are summarized as follows:
BACHAQUERO CRUDE [750 F., 3 hrs. on heat, cc. NHfOH soln. in each cycle] Cycle 6 7 8 9 1O 11 Charge, Grams: I
Asphaltglesi 1.1 i 150 150 150 r 12(5) Methyl ap it a ene. a Recycle Product 450 1 250 435 200 Method of Recovery from Precipitated Auto Soxhlet Extraction 1 without Soxhlet Extraction 2 with Hg elave Prod. H Blanket Blanket Recovered Products, Grams:
IBP-430" F. Naphtha.. 19. 5 12 13. 6 38. 5 7 15. 5 480 F.+ Gas OiL- 111 89 9t 85 57 Residue 50. 5 33 62 9 12 10 Wt. Percent Residue on Asphaltene Charge." 34 22 41 9 12 1O 1 235 grams of asphaltenes recovered from operation similar to Cycle 1. 2 Extracted with methyl naphthalene at about 150-175 F. prior to S operation under hydrogen blanket.
THE RMAL DEPOLYME RI oxhlet extraction at about 450 F.; all
ZATION OF ASPHALTENES, BACHAQUERO CRUDE [3 hours residence time, 720-728 F., autogenous pressure] Recovered Products Feed Asphaltenes 450" F.+ Gas Unreacted Residue Oil Asphaltenes Grams 147 124 39. 9 2. 6 Conradson Carbon, Wt. Percent 15 8 66 1 N.D. Nickel, ppm 300 38 2,000 1 N.D. Vanadium, p.p.m 2, 400 74 4, 000 7, 000
Example 3 A conversion of the Conradson carbon content of the asphaltenes to low Conradson carbon, low metals gas oil is demonstrated. The metals content of the feed is concentrated in the insoluble residue.
Example 5 The features of liquid phase thermal treatment in presence of a solvent essentially in the absence of oxygen, separation of the unreacted material from the lower boiling components, solution of the unreacted material in the Fresh Components Recovered Products Fresh Recycle Asphaltenes Asphaltenes Vanadium, p.p.m
1 N.D.=Not Determined.
Example 4 An operation similar to that of Example 2 was carried out except that no fresh asphaltenes were recharged and the solvent was reagent grade tetralin instead of methyl naphthalene. Starting with a charge of 147 grams of asphaltenes from Bachaquero crude in 394 grams of tetralin the depolymerization was conducted at 728 F. and the autoclave product pentane precipitated, filtered and the gas oil product was recovered from the filtrate. The precipitate was extracted with tetralin in the absence of air, i.e., with a hydrogen blanket, and the extract was removed for recycle leaving the residue on the extraction thimble. A total of four such cycles was made each with fresh tetralinfollowing which the unreacted asphaltenes were recovered for inspection. Of the 147 grams 480 F.+ Recycle Residue Gas Oil Asphaltenes 318 157 31 4 61 1 N.D. 6 a 600 1 N.D. 18 3, 300 37, 000
0 solvent, recovery of the insoluble residue by filtration was followed but with a diiferent feed and a diiferent technique. For this work the tetralin solvent was first freed of peroxides by refluxing in an atmosphere of hydrogen and the water was removed as vapor. The treated solvent was blended with West Texas vacuum bottoms in the weight ratio of 1530/1519. The one liter stirrer autoclave was charged with 504 grams of this mixture and after purging with nitrogen and then with hydrogen, the thermal depolymerization was conducted for 3 hours at 750 F. at autogenic pressure.
The products were flashed from the autoclave first at atmospheric pressure and then at about 0.5 mm. Hg and 450 F. The flashed products were set aside for later workup. The autoclave was recharged with the original mixture of tetralin and the residuum bottoms and tetralin other than that in the blend to compensate for the material removed in the flashing operation and to maintain the same amount of tetralin originally present.
The thermal depolyrnerization was repeated through eleven such cycles. Thereupon, the nonvolatile material remaining in the autoclave was dissolved in tetralin and the solution was removed and filtered. The residue was further extracted with tetralin in Soxhlet equipment and then with benzene to remove the highly boiling solvent. The filtrate and tetralin Soxhlet extracts were combined and were vacuum distilled to yield the 1000 F.+ bottoms. The combined overheads from the flashing of autoclave products and vacuum distillation of the extracts were fractionated in a laboratory column into C -3O0 F. naphtha, 300-400 F. naphtha, 400-450 F. solvent fraction, and 450 F.+ gas oil. This operation is summarized as follows:
liter autoclave and air was expelled by purging with nitrogen and then with hydrogen. The system was pressurized with hydrogen at 500 psig at ambient temperature and was heated to 750 F. and the temperature was maintained at this level for one hour. Thereupon, the products were flashed first at atmospheric pressure which provided a cooling of the autoclave and then at about 0.5 mm. Hg pressure at a temperature of about 600 F.
Methyl naphthalene recovered from a similar operation and refluxed to remove peroxides which may have formed in the interim period was recharged to the autoclave to approximately the same methyl naphthalene content and the operation was repeated. A total of three such cycles were made employing only the original asphaltene charge and the internal recycle of the unreacted portion. The material remaining in the autoclave was suspended in methyl naphthalene and the blend of solution plus solids was filtered under a hydrogen blanket. The filter cake THERMAL DEPOLYMERIZATION OF WEST TEXAS VACUUM RESIDUUM [Tetralin solvent, eleven 3-hour cycles at 750 F.]
Products Residuum Feed (J -300 F. 300-400 F. 450-1000 F. 1,000 F.+ Residue Naphtha N aphtha Gas Oil Unreacted Grams 755 42 73. 8 277 344 Gravity, API 47. 3 23.0 24. 8 Conradson Carbon, Wt. Pereent 16. 5 0 0 0 19. 6 Nitrogen, Wt. Percent 0. 4 0. 13 0. 6 Sulfur, Wt. Percent 1. 2 1. 8 Nickel, p.p.m 1 Vanadium, p.p.rn 1 25 Vol, Percent above 650 F 40 was further extracted with methyl naphthalene and then with benzene to remove the high boiling solvent.
The filtrate and the methyl naphthalene extracts were vacuum distilled to yield the unreacted 1000 F.+ bottoms The combined overhead products from the flashing operations and the vacuum distillation of the filtrate and extracts were fractionated in-a laboratory column (15/5 operation) using 15 theoretical plates at a 5 to l reflux ratio, to yield the naphtha, the solvent and the 485 F.+ gas oil fraction. This is summarized as follows:
THERMAL DEPOLYMERIZATIOIETACZFfiASPHALTENES FROM WEST TEXAS CRUDE-METHYL THALENE SOLVENT [One hour at about 700 p.s.i.g. H partial pressure], 750 F.]
[Maximum total pressure during run=1600 p.s.1.g.
Recovered Product West Texas Asphaltenes 485-1,000 F. Unreacted Solids Residue Gas Oil 1,000 F.+Prod.
Grams 277 99 133 Conradson Carbon, Wt., Percent" 39. 6 0 50. 2 Sulfur, Wt., Percent 5.14 1. 9 4. 94 Nitrogen, Wt., Percent 0.792 0.26 1.13 Nickel, p.p m 1 453 Vanadium, p.p.m 120 1 259 Example 6 A depolymerization is conducted in a manner similar to the method of Example 5, but a different polymeric material (l000 F.+product) and a difierent solvent are employed. For this work five-1000 gram batches of West Texas Atmospheric residuum were precipitated with normal pentane in a 5/1 volume ratio which yielded 357 grams of asphaltenes. This product was vacuum dried and the dried product was maintained under a hydrogen blanket so as to avoid an oxygen uptake from the atmosphere. A solution of 277 grams of these asphaltenes in 351 grams of methyl naphthalene was changed to the one- As in Examples 2, 3, 4, and 5 the recovered gas oil is of much lower sulfur and metals content than the feed. Again the negligible amount of metals in the gas oil makes this product a very good feed for either catalytic cracking or hydrocracking.
What is claimed is:
1. A noncatalytic, liquid-phase process for converting heavy high boiling residua having a relatively high content of sulfur and metals to lower boiling gas oils having reduced sulfur and metals content consisting essentially of the steps of (A) heating an intimate blend of said residua and 0.5 :1
to 5:1 volumes of an aromatic solvent boiling in the 1 11 ran e of 150800 F. at a temperature in the range of 650900 F. and a residence time of 0.1 to 6 hours and (B) separating a low sulfur, low metals gas oil fraction from the reaction mixture,
said steps (A) .and (B) being carried out in an essentially oxygen-free atmosphere.
2. A process as in claim 1 Where said residua has an initial boiling point of about 650 F.+ and a molecular weight ranging from 200 to 20,000.
3. A process as in claim 1 wherein said blend is prepared by heating said residua and said solvent at temperatures of 200 to 450 F.
4. Process according to claim 1 in which the oxygen free atmosphere is obtained by blanketing the process steps with an inert gas.
5. Process according to claim 4 in which the gas is hydrogen.
6. Process according to claim 1 in which the molecular oxygen content of the residua and solvent is less than 0.1 wt. percent based on the blend.
7. A noncatalytic, liquid phase process for converting asphaltenes to gas oil consisting essentially of the steps of (A) separating the asphaltene fraction from heavy high boiling residua,-
(B) heating an intimate blend of said asphaltenes and 0.5 :1 to 5:1 volumes of an aromatic hydrocarbon solvent boiling in the range of 400-600 F. at a temperature in the range of 670775 F. and a residence time of 1-4 hours,
(C) filtering solids from the reaction mixture and recovering a liquid reaction mixture, and
(D) fractionating the liquid reaction mixture to obtain a gasoline fraction, a solvent fraction, and a gas oil fraction having a boiling range of about 430- 1000 B,
said steps (A), (B), (C) and (D) being carried out in an essentially oxygen-free atmosphere.
duced sulfur and metals content consisting essentially of the steps of (A) heating an intimate blend of said residua having an A.P.I. gravity of 200, a molecular Weight of 400600 and an initial boiling point above about 950 F. with 0.521 to 5:1 volumes of an aromatic solvent boiling in the range of ISO-800 F. at a temperature in the range of 650-900 F. and a residence time of 0.1-6 hours,
(B) passing the reaction mixture to a primary separation zone,
(C) separating a fraction boiling above about 1000 F., said fraction containing unreacted material and sulfur and metal compounds,
(D) fractionating the fraction boiling below about 100 FF. to recover gasoline, solvent and gas oil,
(E) dissolving the fraction of Step (C) in the solvent,
(F) recycling the solution of Step (E) to the heating Steps and bfiing carried out in an essentially oxygen-free atmosphere.
9. Process according to claim 8 in which the separation in the primary separation zone consists of precipitation with a C paraffinic hydnocarbon solvent.
10. Process according to claim 8 in which the separation in the primary separation zone consists of vacuum flashmg. References Cited by the Examiner UNITED STATES PATENTS 2,291,337 7/1942 Harvey 208-128 2,336,505 12/1943 Salmi 208-125 2,749,288 6/1956 Watkins 208-125 2,756,186 7/1956 Owen et al 208125 2,782,145 2/1957 Ferris .208l25 2,953,513 9/ 1960 Langer 208-56 2,989,461 6/1961 Eastman et al 208-128 8. A noncatalytic, liquid Phase process for converting high boiling residua having a relatively high content of sulfur and metals to lower boiling gas oils having re- DELBERT E. GANTZ, Primary Examiner.
HERBERT LEVINE, Examiner.