US2952613A

US2952613A - Processing petroleum oils

Info

Publication number: US2952613A
Application number: US571168A
Authority: US
Inventors: Elmond L Claridge
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1956-03-13
Filing date: 1956-03-13
Publication date: 1960-09-13
Anticipated expiration: 1977-09-13

Description

Sept 13, 1960 E. L. CLARIDGE v 2,952,613

PROCESSING PETROLEUM-OILS Filed March 13, 195s 2 Sheets-Sheet 1 zumzuazoo ...o mg w INVENTOR ELMOND L. CLARIDGE HIS AGENT Sept' 13 1960 E. L. CLARIDGE- 2,952,613Y

PROCESSING PETROLEUM OILS 2 Sheets-Sheet 2 Filed' March l5, 1956 INVENTOR hm wm E LMOND L. CLARIDGE HIS AGENT United States Patent Oiiice 2,952,613 Patented Sept. 13, 1960 2,952,613 PROCESSING PETROLEUM OILS Elmond L. Claridge, Houston, Tex., assigner to Shell Oil Company, New York, NX., a corporation of Delaware Filed Mar. 13, 1956, Ser. No. 571,168 9 Claims. (Cl. 208-73) This invention relates to a petroleum refining process. More particularly, it relates to an improved process for the preparation of catalytic cracking `feed stock from petroleum oils which contain asphaltic constituents, such as crude petroleum, partially reduced crude oil, or the like.

Various methods have been proposed and utilized for the recovery of clean oils and fractions thereof from crude oil, topped crude oil, reduced crude, ,and the like. Thus, atmospheric and vacuum distillations, as well as steam distillation, without cracking and sometimes with mild thermal cracking, yas in visbreaking, are Well known commercial methods lfor :the production of =various distillates, such as gasoline, kerosene, light gas oil, heavy gas oil and distillate lubricating oils. On the other hand, the asphaltic and resinous bodies present in varying amounts in different crude oils have been separated by precipitation from the oil with light hydrocarbons, such as in propane deasphalting operations, to yield a deasphalted oil, which, in many cases, is more or less equivalent to distillate fractions, such as a vacuum flashed distillate, as catalytic cracking feed material. However, the previously available methods, particularly when applied to oils which contain appreciable amounts of asphaltic material and metal contaminants, have suifered from the defect of not providing maximum yields of catalytic cracking -feed stock While at the same time maintaining the oil at a high quality level for its use in the catalytic cracking operation. Consequently, it -has been necessary .to process more crude oil to provide the necessary amount of catalytic cracker lfeed stock of suitable high quality, or it has been necessary to reduce the oil throughput of the catalytic cracking unit because of :the reduced activity of the catalyst caused by the poorer quality of the cracking feed stock and the concomitant increase in coke make in the reaction zone with resulting greater demand in the regeneration zone for burning olf the coke on the catalyst.

It is a principal object of the present invention to provide an improved process for the production of catalytic cracking feed stock in enhanced yield and of improved quality from a crude oil which contains asphaltic constituents. A more specific object is to recover catalytic cracking feed, from straight run residue or vacuum asher pitch, `at higher yields and of better quality. It is a further object to provide a process for the production of higher yields of catalytic cracking yfeed from asphaltic residues, while at the same time producing an asphalt of good quality. These objects will be more fully nnder stood |and others Will become apparent from the description of the invention, which is made with reference to the accompanying drawing, wherein:

Fig. I is a process design representing a suitable plant scheme for 'the practice of the invention; and

Fig. Il is a diagrammatic sketch of another process design for the production of catalytic cracking feed stock :from -a reduced crude.

It has now ybeen discovered that an increased yield of high quality cracking feed can be obtained from reduced crude oil containing asphaltic, resinous and metal-containing contaminant constituents, by a coordinated combination of operations wherein: (l) reduced crude is treated with a deasphalting solvent under conditions controlled to separate only a portion of the oil components and only a minor proportion of -the metal-containing contamin-an-ts in `a separate oil-solvent phase from the asphaltic constituents; (2) the oily asphaltic residue is then mildly thermally treated to crack only a minor proportion of the oil components while converting metalcontaining constituents `to less volatile and less oil-soluble constituents and cracking some of .the asphaltic (aromatic) components to produce parainic oil components; and (3) recovering a further amount of oil components from the asphaltic residue by extraction with a low molecular Weight hydrocarbon.

In accordance with a more particular and preferred embodiment of the invention, the process comprises: (d) removing a substantial portion of the distillable catalytic crackin-g feed oil components from the reduced crude by vaporization at a low subatrnospheric pressure, such as by a vacuum flashing, while .avoiding thermal cracking; (2) extracting the residue from this partial vaporization separation with a light hydrocarbon deasphalting solvent and recovering a predominantly propane-soluble catalytic craking feed oil from `the solvent extract; (3) thermally cracking the asphaltic residue from the extraction, thereby converting metal-containing components to less oilsoluble metal-containing substances and cracking asphaltic components to produce paranic oil components; (4) extracting [the cracked product with a light hydrocarbon .deasphalting solvent to recover a further amount of propane-soluble components; yand (5) recovering predominantly propane-soluble catalytic cracking feed oil components from .the resulting solvent extract. A still further preferred practice of the invention comprises recycling to the thermal crackin-g step (3) immediately above at least a portion of a propane-insoluble fraction which is separated from propane-soluble components in solvent extraction and recovery steps (4) and (5).

Thus, the process comprises at least two solvent deasphalting operations on the heavier asphaltic residual material with an intervening mild thermal cracking of at least once-deasphalrtized material. The two deasphalting operations on the heavier fraction of material can be carried out in separate deasphalting zones, or in the same zone at separate times, or in the same zone at the same time.

The rst solvent deasphalting operation is carried out -under conditions of temperature, pressure, solvent-to-oil ratio, and the like, as will be well understood by those familiar with solvent deasphalting lof asphaltic oils, to effect a separation of only a portion of the oil, such that the metal contaminants content thereof is maintained at a suitably low value. In general, the more paraiiinic oil components will be extracted While a substan-tial proportion of the more aromatic and higher boiling oil components will remain with the asphaltic residue. The extent of the extraction in general will be limited at this stage to that which is extractable with propane alone, although -it is not required that the solvent be propane alone. -Not only do the oil .components thus recovered, having for the most part molecular weights up `to about 500, have superior catalytic cracking properties, but the low concentration of metal-containing contamina-nts minimizes the poisoning effect thereof on the catalyst, as well as Ithe tendency to increase coke .formation during the catalytic cracking.

The mild thermal cracking of the partially de-oiled asphaltic residual material serv the multiple purpose of: (a) converting high molecular Weight oil components to lower molecular weight oil components of improved catalytic cracking characteristics; (b) producing suitable catalytic cracking oil feed components by cracking higher alkyl substituents from polynuclear asphaltic or resinous substances while at the same time producing ya molecular residue of reduced solubility in deasphalting solvent there` deasphalting. The oil components in the oily asphalt feed to the mild thermal cracking also serve a diluent purpose in minimizing extensive condensation of dealkylated asphaltic type molecular `residues to coke or cokelike bodies.

The exact set of conditions which is optimum for the mild thermal cracking depends on a number of factors, such as the nature of the heavy oil stock and other correlative conditions in the combination of operations. In general, the temperature suitably ranges from about 400 C. to about 500 C., the residence time from a few seconds to about 60 minutes, and the pressure from substantially atmospheric to a substantially superatmospheric pressure, which can be as high as 300-500 p.s.i.g. or evenhigher, although a pressure of from about 1 atmosphere to about 200 p.s.i.g. is preferable. It will understood that the higher temperatures are used at the shorter residence times, and vice versa. The conditions will usually be selected to limit the cracking of the material t gas and gasoline components to not over about 10% by weight, based on the material subjected to the thermal cracking, and suitably not over about 5 The lighter cracked products, such as the gas and gasoline components, and usually the lighter gas oil fraction, particularly those components lighter than the lightest oil in the feed to the first deasphalting operation, may be advantageously removed by distillation and/or flashing prior to subjecting the material to the subsequent deasphalting operation for the recovery of a further amount of catalytic cracking feed oil.

When the second deasphalting step is carried out separately from the iirst one, a deeper extraction of oil can be made without adversely affecting the quality of the recovered oil. As already pointed out, the thermal cracking has the effect of reducing the solubility of both the coke-forming asphaltic `and resinous components and of the metal-containing components, so that more complete solution of the oil components in the solvent can be effected without dissolving an undesirable proportion of the deleterious materials.

'In accordance with a further aspect of the invention, at least a portion of the heavier or less propane-soluble oil components of the thermally cracked product is subjected to a still further mild thermal cracking, preferably by recycling it to the previous cracking zione in admixture with other uncracked material. This is readily accomplished when the later deasphalting operation is accomplished in the first deasphalting` zone simultaneously with the first deasphalting step. In that case, a portion of the asphaltic residue, comprising a blend of cracked and uncracked asphaltic components is suitably withdrawn as an asphalt product, if desired or necessary, in order to prevent tooimuch build-up of higher melting asphaltenes in the recycling stream. When the two deasphalting operations are separate, the heavier or more aromatic portion of the deasphalted oil from the later deasphalting can be advantageously recycled to the thermal cracking zone, or it, with or without other oil components, can be recycled to the previousl deasphalting step. When recycling the heavier components of the oil to the thermal cracking zone, the second deasphalting operation, when carried out separately, can be carried out to the extent of deliberately including some of the more oil-soluble metalcontaining materials and asphaltic bodies in the extract, since they will be converted to separable components by the subsequent thermal treatment thereof.

Having described the general nature of the invention I based on the feed' to the heater (cracker).

and various features thereof, its practice will be more readily understood from more detailed description of particular embodiments of it.

Referring specifically to Fig. I, a reduced crude, such as the bottoms from a Los' Angeles' Basin crude which has been distilled to" remove the usual gas, light naphtha, heavy naphtha and gas oil fractions, as feed in line 11 isheated to hashing temperature by passage through a suitable furnace 12, such as a coil or tube heater, and delivered by line 14 to a suitable flashing tower 15 provided with suitable vapor-liquid separating means, such as bubble-cap trays,.grid trays, or the like, from which a portion of the-distillable oil components is removed as an overhead flasher distillate in line 16 while theremainder. is removed as a bottoms asher pitchvin line 17. Althoughit is desirable to recover the maximum of distillate oil in this operation, a substantial proportion of distillable oil is invariably -left in the pitch in commercial operations.

Although it is advantageous with many crude oil stocks to remove a portion of the heavier distillable oils, `as by vacuum hashing, in order to make the subsequent extraction with a light hydrocarbon more effective, it is not necessary -to do so in all cases. Hence, as indicated, the flasher pitch in line V17 may be utilized alone or admixed with a portion of reduced crude in line 19, or the vacuum flashing operation may be by-passed entirely. The flasher pitch and/or reduced crude in line 19 is delivered to a suitable solvent extraction zone, as in extractor 20 Wherein it is intimately contacted, as by countercurrent flow, with a suitable selective solvent for the oil but a nonsolvent for asphaltic material, as well-known in the art, such. as the lower molecular weight hydrocarbons. Propane or butaneland mixtures thereof are well suited to the purpose. The details 'of temperature, pressure, solvent-tooil ratios, and the like, of such s o-called deasphalting operations are well understood in the art. B'y the use of propane or propanev-'butane mixture, a substantial portion of the oil content is readily recovered while leaving a substantial portion in the residue. The extraction conditions are selected so that the recovered oil, for the principal part, is made up of substances of molecular Weights below about 500. By thus controlling the separation, the total metals content of the oil is kept below about parts per million as metal.

A The C3/C4 solvent, introduced by line 21, is removed for the most part with oil in line Z2, the remainder being removed in line 24 with the remaining partially deoiled asphaltic residue. The reduced crude and/ or flasher pitch may be suitably extracted in extractor 20 in admixture with thermally cracked asphaltic residual material, as produced at a.v later stage in the operation, delivered by line 25 to line 19 and/or line 25'.

The solvent-oil extract in line 22 is then stripped in stripper 26 to recover the solvent `as an overhead product which is suitably condensed in condenser 27 fand collected in surge drum 29, from which a portion is returned to the stripper to provide `relux and the remainder is recycled by

lines

30 and 21 tothe'extractor 20. Any lighter gases are readily removed by line 28 While lighter oils (na-phtha), which will be present if the total subsequently cracked product stream isrecycled to extractor20, may bey readily withdrawn as one or more Sidestreams as by line 33. The stripped oil is withdrawn through line 31 and may be combined-in line 16 with oil from the vacuum lasher 'tofprovide an enhanced yield of high quality catalytic cracking feed stock V VThe propone-butano in the partially deoile'd asphaltic residue in -line24 is stripped therefrom in stripper 32 and returned by

lines

34 and 21 to the extractor. The stripped residue is withdrawn in line 35 and heated in heater 36 Ato effect a minor amount of thermal cracking Vequivalent to the production of from about 10% to about 30% by weight of material boiling up to labout 400* F.,

'Ihe thermal-ly cracked residue is then further" extracted by light hydrocarbon, as by recycling it by

lines

37, 25 and 19 to extractor 20, or it can be extracted in a separate extractor 39, to which iall of it is delivered directly through line 40 and cooler 41. On the other hand, the cracked product stream from heater 36 can be delivered by

lines

37 and 42 to a suitable fractionator 44, wherein lighter cracked products are separated as one or more distillate fractions, withdrawn by

lines

45, 46, 47 and 49, as desired, and the topped oily asphaltic residue Withdrawn through line 45 and delivered either by line 25 to extractor 20 or by line 40 to extractor 39. When it is -further extracted in extractor 20, a portion of the partially deoiled residue from stripper 32 will be withdrawn via line 62 to provide for constant removal of ultimate residue from the system.

Extraction of the cracked residue in extractor 39 may be carried out with a further portion of the same hydrocarbon or hydrocarbon mixture used in the Iirst stage extraction in extractor 20. However, a more complete recovery of the oil as well as of oil precursors is more readily secured by the use of a higher boiling hydrocarbon or mixture thereof, such as pentanes or hexanes, or a mixture of CB-Cq hydrocarbons having an average molecular weight of about that of the pentanes.

The extract removed overhead by line '50 is stripped of solvent, and of any lighter hydrocarbons, in stripperfractionator 51, any naphthas suitably withdrawn as one or more sidestreams, as indicated by lines 52 and 54, and the heaviest portion of the oil, containing coke-forming and metal-containing components, withdrawn as a bottoms fraction. Recovered solvent is recycled to the extractor through condenser 55, surge tank 56 and lines 57 iand 59. The bottoms fraction in line 60 from 51 may be subjected to a further thermal cracking, as by recycling it to heater '36, to condition it for recovery of a further amount of suitable oil from it. However. a portion or -all of it may be delivered by line 61 to line 62 for blending with the final residue which is withdrawn from the process.

The deoiled residue from extractor 39 is delivered by line 64 to stripper 65, from whence recovered solvent is returned by lines 66 and 59 to the extractor and stripped residue is delivered to line `62.

Referring to Fig. 1I, ka straight run residue (reduced crude) is delivered by line 81 to a heating coil 82 in furnace 84, then by line 85 to a Vapor-liquid flash separation section of a ashing tower 86, having lower and intermediate stripping sections and upper rectifying and condensing sections. 'Ihe light tops are removed as an overhead vapor stream in line 87, condensed in condensers 89 and collected in vessel 90, from whence they are taken as catalytic cracking feed stock. Heavy tops `are withdrawn by line 91 as a sidestream from a trapout tray between the condensing and rectifying sections of the tower, portions being returned above Iand below phalting tower 97. 'Ihe tower 97 is provided at an intermediate level with a plurality of suciently extended upright risers 99 extending through and above a hori- '55 the withdrawal point to provide condensation and reflux, Y

zontal partition member 100, which provides a collecting n zone for partially deoiled asphaltic residue While lighter v i liquid phase from the lower section is permitted to enter through the risers. Thus, the partial separation of oil and asphalt from the stream from line 92 is effected in the presence of an extract phase obtained by extraction of a cracked product from subsequent thermal cracking of the partially deoiled asphaltic residue recovered from the lirst stage (upper section) extraction in tower 97, as described later.v

The asphaltic phase which collects on the partition l100 is withdrawn by line 101, heat exchanged in heat exchanger 102, stripped of solvent, C3/C4 mixture, in asphalt stripper 104, as by the use of open steam, thermally cracked in cracking coil of furnace 84 and delivered by line 106 to ia lower vapor-liquid ash separation zone in tower 86, located between the lower and upper stripping sections. The vaporized material, together with any steam injected in the bottom stripping section, passes upward through the risers provided in the partition separating the lower and upper stripping sections. The liquid product, after stripping it in the lower section, is collected by extended upright downcomers in the bottom of the tower. This partially deoiled cracked residue is delivered by line y107 and through heat exchangers 102 vand 109 and cooler 110 to the lower extraction section of deasphalting tower 97 wherein it is extracted with propane-butane (C3/C4) mixture, with the extract phase being delivered to the upper extraction section through risers 99. By this combination of operations, less desirable oils which are extracted from the cracked residue in the lower section are precipitated as part of the asphalt phase in the upper section, with resultant recycle of them to the cracking step.

'Ihe resulting extract phase is withdrawn from tower 97, through line 1.11, heat exchanged in

exchangers

109 and 95, and stripped of CB/C., in oil stripper 112, with steam, to yield a deasphalted oil in high yield and of good quality as a catalytic cracking feed stock.

The deoiled cracked asphaltic residue from the extraction in tower 97 its withdrawn from the bottom by line 1l14, heat exchanged in exchanger 94 and steam stripped in asphalt stripper 11'5, to remove the solvent, with the asphalt being removed by line 116.

Although the placement of auxiliary equipment has been indicated to some extent, some of it has been omitted in order to simplify the drawing and the description of the invention. The placement of various other required or desirable pieces of equipment, such as pumps, valves, compressors, liquid level control devices, ow rate control devices, temperature recorders and control devices, condensers, reboilers, surge and storage tanks, and

by a mixture of deasphalting solvent (such as liquid VCa/C., mixture) and partially or wholly cracked oil derived from deasphalting of cracked residue in a lower section of the deasphalting tower.

A further understanding of various factors involved in the practice of the invention will be had from a consideration of the results to be described with reference to the processing of a reduced crude from Los Angeles Basin crude oil. The properties of a typical asher pitch withdrawn from a commercial vacuum ilasher, operating yon Los Angeles Basin reduced crude in the preparation 'of distillate feed stock for a commercial catalytic cracker, are given in Table l.

Table 11 .-Properties of flasher pitch Refractive index, n (70 C./D) 1.570

Viscosity, 210 F.:

Centistokes 2060 Saybolt seconds Furol 973 API gravity, 60/60 F 7.3

Density:

Y9 higher than those for propane. Although the oi-l yields depend on the solvent used, other factors being constant, selectivities, as indicated by coke values, were essentially the same at equal solvent/ feed ratios.

Comparisons have been made between distillates obtained from secondary ashing of the flasher pitch and oil obtained by extraction. The superiority of extracted product as compared to flashed product from pitch becomes less as increased yields (deeper extraction) are obtained. This is indicated qualitatively by the visual observation that oils from propane extraction (deasphalting) produced at low yields are much lighter in color than corresponding ashed products, Whereas isopentane extracted oils are somewhat darker in color than cor- `responding flashed products.

As stated previously, the oil recovered inthe first stage extraction for catalytic cracking feed is preferably restricted substantially to that which is extractable with propane alone, so as to maintain it at a high quality level. The same principles apply as well to the subsequent extractions. However, wvhen the subsequent extraction is a separate extraction for maximum oil recovery, Iwith separation Of the heavier fraction thereof, as by distillation, and further thermal cracking of it to yield more catalytic cracking feed stock, the extraction is advantageously carried out with a higher hydrocarbon (C4-C7) and under conditions to recover the low quality oil components as Well.

The advantage of butane extraction of a ilash cracked residue over extraction of flasher pitch, both at the same yield, is shown by the improved quality of the deasphalted oil in the former case. For the same quality of oil, the former combination yields the larger volume of oil. The results of extraction of a mildly thermally cracked pitch remaining after ashing olf 36.7% by Weight light products, and of a =asher pitch remaining after ashing on 39.1% by Weight of distillate, both from i given 1n Table 4.

Table 4.-Deasphaltlng asher pitch and flash cracked reszdue from LA. Basin residue Charge to Deasphalting Flash Cracked Flasher Pitch Residue DA Run No A B C D DA Conditions:

Solvent n-C4 n-C4 n-C4 n-C4 Solvent/Feed Ratio, vol 3. 36 2. 82 3. 06 3. 97 Column Temperature, C.:

p 129. 5 121. 1 115. 5 121 Bottom- 131. 1 121. 1 115. 5 110 Pressure p.s. 525 525 530 395 DA Oil Properties:

API Gravity at 60 F 14. 8 14. 4 13. 3 14. 2 Viscosity, SSU at 210 F 213 233 624. l 448. 3 Ramsbottom Carbon Residue,

Percent W 7. 19 7. 29 Sulfur, Percent W.- 4. 61 2. 25 Total Metals, p p m NH-V, p.p.m 102 79 Refractive Index, m70. 1. 5274 Asphalt Properties:

Penetration, d.m.m. at 77 F 0 0 0 0 softening Point, F 325+ 325+ 299 268 Specific Gravity 1.135 1.125 1.0824 1. 0973 lYields, Percent v., Basis SR Residue: 1 Gasoline-Free Distillate. 33. 6 33.6 40. 3 40. 3 DA Oil 43. 3 46. 3 43.0 39. 7 Asphalt 18. 2 15.0 15. 3 18. 6

It will be seen that for the same asphalt yield, at two yield levels, the deasphalted oil from the combination of flash cracking plus deasphalting is a superior catalytic [cracking feed.

The properties of the gasoline-free distillates in Table 4 are given in Table 5, showing marked reduction in metals content of the ash cracked distillate.

separate portions of the same straight run residue, are.

Table 5 .-Propei'tz'es of gasoline-free dz'stillates from flashing and flash cracking of LA. Basin straight run residue The following exemplary processing conditions for a Los Angeles Basin stock are further illustrative of but not limiting on the invention: A 50% topping residue is prepared by the usual distillation topping procedures utilized in the typical reiinery. This residue is then vacuum -ashed to produce 43% by weight thereof as flasher pitch having a 7.8 API gravity, a 5,000 SSU Viscosity at 210 F. and containing 240 p.p.m. of nickel and vanadium, expressed as metal. This ilasher pitch is fed to a deasphalting unit using 400% by Volume of 50-50 C3- and C4-hydrocarbons, based on the flasher pitch. The lower temperature conditions are adjusted to get about 50% of the ilasher pitch as asphalt bottoms containing -98% of the metals content of the pitch and having a softening point of 250 F. This asphalt is then mildly cracked under conditions to give a substantially lower softening point of the product and to convent the metals toa less soluble form. The mildly cracked asphaltic product is fed to va second deasphalting tower, taking about 50% as bottoms thereof land retaining the major portion of the metals therein.

I claim as my invention:

l. A process for the production and recovery of catalytic cracking feed stock from a reduced crude containing asphaltic and metal-containing constituents and an oil portion which comprises: (l) solvent extracting the reduced crude with a light hydrocarbon deasphalting solvent made up of essentially propane to obtain a solvent extract phase and an asphaltic residue containing an appreciable portion of the oil yand a major portion of the metal-containing constituents and recovering predominantly propane-soluble catalytic cracking feed oil components from the solvent extract phase; (2) non-catalytically thermally cracking the asphaltic residue resulting from the extraction at a temperature within the range of about 400 C. to about 500 C. for a period of time selectively chosen within the range of about a few seconds to about 60 minutes so that only mild thermal cracking can take place Without the occurrence of appreciable coking, thereby converting the metal-containing components to less oil-soluble metal-containing substances and cracking the asphaltic components to produce paraflinic oil components; (3) extracting from the cracked product by means of the addition of a light hydrocarbon deasphalting solvent comprising essentially a C4-C7 hydrocarbon a further amount of propane-soluble components; and (4) recovering predominantly propane-soluble catalytic cracking feed oil components from the resulting solvent extract.

2. A process for the production and recovery of catalytic cracking feed stock from a reduced crude containing asphaltic and metal-containing constituents and an oil portion which comprises: (1) solvent extracting the reduced crude with a light hydrocarbon deasphalting solvent comprising essentially propane to obtain a solvent extract phase and an asphaltic residue containing an Iappreciable proportion of the oil and a major proportion of the metal-containing constituents and recovering predominantly propane-soluble catalytic cracking feed oil components from the solvent extract phase; (2) noncatalytically thermally cracking the asphaltic residue resulting from the extraction at a temperature within the 11 range of about 400 C. to about 500" for a period of time selectively chosen from the range of about a few seconds to about v60 minutes so that only a mild thermal cracking can take place Without the occurrence of ap-Y preciable coking, vthereby converting the metal-containing components'to less oil-soluble metal-containing substances and cracking the asphaltic components to pro-v duce paranic oil components; (3) extracting from the cracked product by means of the addition of a light' rived from the extraction of step (3) to the thermalj cracking step (2). Y

3. An integrated process for the handling of -a reduced crude containing asphaltic and metal-containing constituents and an oil portion to produce a quality asphaltY and involving the preparation and catalytic cracking of a feed stock derived in an enhanced yield from said reduced crude which comprises (l) solvent extracting the reduced crude with a light hydrocarbon deasphalting solvent to obtain a solvent extract phase and an asphaltie residue containing an appreciable portion of the oil and a major proportion of the metal-containing constituents and re-l covering predominantly propane-soluble catalytic cracking feed oil components from the solvent extract phase; (2) non-catalytically thermally cracking at least a portion of the asphaltic residue resulting from the extraction at a temperature within the range of about 400 C. to about 500 C. for a period of time selectively chosen from the range of about a few seconds to about 60 minutes so that only mild thermal cracking can take place without the occurrence of appreciable coking, thereby converting the metal-containing components to less oilsoluble metal-containing substances V'and cracking the asphaltic components to produce paranic oil components; (3) extracting from the cracked product by means of the addition of a light hydrocarbon deasphalting solvent a further amount of propane-soluble components; (4) recovering predominantly propane-soluble catalytic cracking feed oil components from the resulting solvent extract of step (3); (5) subjecting the recovered propane- 12 soluble catalytic cracking feed oil components to catalytic cracking without vinitially hydrogenating .said feed oil components and(6) 'continuously removing from the process a quality asphalt product previously separated from the catalytic cracking feedoil components.

4. A process inaccordance with claim 1, wherein the light hydrocarbon solvent used in steps (1) and (3) comprises a substantial proportion of propane. Y

5. A process in accordance with claiml, wherein yat least a portion ofthe propane-insoluble metal containing and aromatic components, from which propane-soluble components are separated in steps (3) and (4), is re cycled to the thermal crackingstep (2).

6. A process in accordance with claim 1, wherein the light hydrocarbon solvent used in steps (1) and (3) comprises a substantial proportion of propane, and wherein the resulting asphalticv residue from the extractionin step (3) is recycled in part to the thermal cracking step (2). Y

7. A process in accordance with claim 1, wherein the reduced crude which is solvent extracted in step (l) is one from which a substantial portion of distillable catalytic cracking feed oil components has been removed by vaporization at a'low subatmospheric pressure while avoiding thermal cracking.

8, A process in accordance with claim 1, wherein the solvent extracting steps (l) and (3) 'are carried out by countercurrently contacting the extracting agent and the material being extracted, and wherein the extracting agent I and oil ldissolved therein in step (3) is delivered to step (l) as source of extracting agent.

9. A process in accordance with claim 3, wherein the` light hydrocarbon solvent used in steps (1) and (3) is essentially propane and wherein the thermal cracking is carried out at a pressure from about 1 atmosphere to about 500 p.s.i.g.

References Cited in the le of this patent UNITED STATES PATENTS 2,222,060 vArveson Nov. 19, 1940 2,559,285 Douce July 3, 1951 2,696,458 Strickland Dec. 7, 1954 2,727,853 Hennig Dec. 20, 1955 2,854,398 Knox Sept. 30, 1958

Claims

1. PROCESS FOR THE PRODUCTION AND RECOVERY OF CATALYTIC CRACKING FEED STOCK FROM A REDUCED CRUDE CONTAINING ASPHALTIC AND METAL-CONTAINING CONSTITUTENTS AND AN OIL PORTION WHICH COMPRISES: (1) SOLVENT EXTRACTING THE REDUCED CRUDE WITH A LIGHT HYDROCARBON DEASPHALTING SOLVENT MADE UP OF ESSENTIALLY PROPANE TO OBTAIN A SOLVENT EXTRACT PHASE AND AN ASPHALTIC RESIDUE CONTAINING AN APPRECIABLE PORTION OF THE OIL AND A MAJOR PORTION OF THE METAL-CONTAINING CONSTITUENTS AND RECOVERING PREDOMINANTLY PROPANE-SOLUBLE CATALYTIC CRACKING FEED OIL COMPONENTS FROM THE SOLVENT EXTRACT PHASE, (2) NON-CATALYTICALLY THERMALLY CRACKING THE ASPHALTIC RESIDUE RESULTING FROM THE EXTRACTION AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 400*C. TO ABOUT 500*C. FOR A PERIOD OF TIME SELECTIVELY CHOSEN WITHIN THE RANGE OF ABOUT A FEW SECONDS TO ABOUT 60 MINUTES SO THAT ONLY MILD THERMAL CRACKING CAN TAKE PLACE WITHOUT THE OCCURRENCE OF APPRECIABLE COKING, THEREBY CONVERTING THE METAL-CONTAINING COMPONENTS TO LESS OIL-SOLUBLE METAL-CONTAINING SUBSTANCES AND CRACKING THE ASPHALTIC COMPONENTS TO PRODUCE PARAFFINIC OIL COMPONENTS, (3) EXTRACTING FROM THE CRACKED PRODUCT BY MEANS OF THE ADDITION OF A LIGHT HYDROCARBON DEASPHALTING SOLVENT COMPRISING ESSENTIALLY A C4-C7 HYDROCARBON A FURTHER AMOUNT OF PROPANE-SOLUBLE COMPONENTS, AND (4) RECOVERING PREDOMINANTLY PROPANE-SOLUBLE CATALYTIC CRACKING FEED OIL COMPONENTS FROM THE RESULTING SOLVENT EXTRACT.