Abstract: A process for separation and removal of stable polycyclic aromatic dimer foulants from refinery process streams by blending a paraffinic stream with a portion of heavy effluent from a hydrocracking reactor to induce precipitation of foulant, which may then be separated and removed from the hydrocracker. Additional embodiments include introduction of flocculating agents and adjusting the temperature of the blend.

Abstract: The inventive solvent extraction process uses hydrotreated (HTR) and low sulfur (LSR) resids feedstreams in a single deasphalter unit and in a way that optimizes the disposition of the oils, resins, and asphaltene fractions of each resid for downstream processing. After the refractory asphaltenes are separated from the HTR feedstream, the LSR resid is introduced into the deasphalter so that its resin and asphaltene fractions are combined with the HTR resins. The oils fractions from the two resids are combined and then used as a feedstock for catalytic cracking.

Abstract: The benzene content of hydrocarbon gasolines is accomplished by (a) fractionating at least one hydrocarbon gasoline into a light fraction A, with an increased benzene content, and a heavy fraction B, with a reduced benzene content; (b) contacting the light fraction A at a temperature below room temperature with a gas containing at least a fraction of olefins in which the number of carbon atoms is from 2 to 5 per molecule so that at least a fraction of said olefins is absorbed in light fraction A; at the end of stage (b), separating a residual gas with a reduced olefin content from a liquid fraction C, with an increased olefin content; (d) passing the fraction C from stage (c) into an alkylation reactor so that at least a fraction of the benzene is alkylated by at least a fraction of the olefins; (e) fractionating the mixture emerging from stage (d) so as to produce, firstly, a gas phase chiefly comprising gases which were not converted during stage (d) and, secondly, a liquid phase, at least partly containing

Abstract: A process is provided for producing a high quality lubricating oil base stock in increased yield. The process includes a hydrocracking step employing a catalyst composition comprising a zeolite of the faujasite type, e.g., zeolite USY, possessisng a silica:alumina ratio of at least about 50:1, and a hydrogenation component.

Abstract: The invention reduces cracking catalyst fines in decanted oil by mixing the decanted oil (DCO) containing cracking catalyst fines with a resid oil and then treating the DCO-resid mixture with a non-aromatic hydrocarbon solvent in an extraction unit or in a multi-stage deasphalting unit.

Abstract: The invention reduces cracking catalyst fines in decanted oil by mixing the decanted oil (DCO) containing cracking catalyst fines with asphaltene and then treating the DCO-asphaltene mixture with a non-aromatic hydrocarbon solvent in an extraction unit or in a multi-stage deasphalting unit.

Abstract: Hydrocarbon lubricants having a high viscosity index (V.I.) and low pour point are produced by hydroisomerizing a waxy lube feed such as slack wax or a waxy gas oil over zeolite beta after which aromatic components are removed by extraction, e.g. with furfural. The raffinate is then dewaxed, preferably by solvent dewaxing to target pour point with a final hydrofinishing step. The hydroisomerization coupled with the aromatics extraction and dewaxing increases the range of crudes that can be processed into high V.I. lubes while maintaining equivalent product qualities. Hydrogen consumption in the process is relatively low.

Abstract: A method for stabilizing oil is provided. An oil fraction having hydrocarbons with an initial boiling point of about 200.degree. F. to about 1050.degree. F. is hydrotreated to reduce the nitrogen content of the oil fraction to be stabilized. Subsequently, condensed aromatic compounds are selectively extracted from the hydrotreated oil fraction to yield a stable oil fraction.

Abstract: Non-carcinogenic bright stock extracts and/or deasphalted oils are produced from reduced hydrocarbon feedstocks. Such non-carcinogenic products are produced by establishing a functional relationship between mutagenicity index and a physical property correlative of hydrocarbon type for the bright stock extract or deasphalted oil and determining a critical physical property level which, when achieved, results in a product having a mutagenicity index of less than about 1.0. Process conditions are established so that a product stream achieving the desired physical property level can be produced. Non-carcinogenic bright stock extracts and/or deasphalted oils are then processed utilizing the conditions so established. A bright stock extract and a deasphalted oil substantilly free from mutagenic activity, as well as processes for their production are also provided herein.

Abstract: Heavy hydrocarbon oil, containing asphaltene, sulfur and metal contaminants, is hydrotreated in the presence of a hydrotreating catalyst having a small pore diameter in an initial process step to remove sulfur and metal contaminants. Removal of additional metal and sulfur contaminants is then accomplished in a second process step by solvent deasphalting, wherein the size of the pore diameter of the hydrotreating catalyst utilized in the initial hydrotreating step affects the metals rejection in the subsequent solvent deasphalting step. In a third process step the deasphalted oil is catalytically cracked substantially in the absence of added hydrogen to provide lower boiling hydrocarbon products.

Abstract: The invention relates to a process for hydrocarbon fractionation and extraction making it possible to obtain a petrol with an improved octane number and a kerosene with an improved smoke point.According to the invention a charge with a final boiling point of at least 220.degree. C. is fractionated into three fractions:a light petrol containing less than 10% aromatics and boiling points at 25.degree. to 80.degree. C.,a medium petrol (80.degree. C. and at the most 150.degree. C.), whose end point is determined by a nitrogen content below 50 ppm,a heavy petrol with an end point equal to or below 220.degree. C.,be a selective liquid solvent aromatics are then extracted from the heavy petrol producing a refined product which is poured into the kerosene pool or diesel fuel,the solvent is regenerated by reextraction using light petrol so as to produce an aromatics-enriched petrol fraction with an improved octane number.

Abstract: Hydrocarbon feeds are dewaxed and hydrotreated in a two-stage dewaxing-hydrotreating reactor system with interstage separation of olefinic and naphtha and light olefins. Separation of the naphtha and olefins is carried out by stripping the effluent from the dewaxing reactor with a stripping medium such as make-up hydrogen or vapor from the hydrotreater effluent. Hydrogen recycle for the dewaxer and the hydrotreater is taken from the stripper/separator after removal of the olefinic naphtha and removal of contaminants. Separation of the lighter olefins from the olefinic naphtha may be improved by the use of an oil solvent such as naphtha introduced into the top of the interstage stripper/separator so that the recycle gas from the stripper/separator is essentially free of wet gas and heavier fractions.

Abstract: A hydrotreating process if provided in which resid and resins are hydrotreated with hydrogen-rich gases in the presence of a hydrotreating catalyst in an ebullated bed reactor.

Abstract: A process for preparing a pipelineable oil from a heavy crude oil by thermally treating the oil in the absence of added hydrogen, and under sufficiently severe conditions to induce the formation of an upgraded, low viscosity oil phase and a liquid asphalt phase that contains dispersed coke. The reaction is conducted under pressure sufficient to retain in the reactor most of the normally liquid hydrocarbons, under which conditions the two phases are readily separated and recovered solely by gravity settling. The process is readily adapted to oil field use with skid mounted units. The severity is adjusted to provide sufficient asphalt which, when burned, furnishes the steam required for production of the heavy crude oil.

Abstract: Lubricant basestocks of high viscosity index, typically with V.I. of at least 130 or higher, and low pour point, typically below 5.degree. F., are produced by hydroisomerizing petroleum waxes such as slack wax or de-oiled wax, over zeolite beta and then dewaxing to target pour point. A preferred process employs a solvent dewaxing after the hydroisomerization step to effect a partial dewaxing with the separated waxes being recycled to the hydroisomerization step; dewaxing is then completed catalytically, typically over ZSM-5 or ZSM-23.

Abstract: A process is disclosed for fractionating lignocellulosic materials fast-prolysis oils to produce phenol-containing compositions suitable for the manufacture of phenol-formaldehyde resins. The process includes admixing the oils with an organic solvent having at least a moderate solubility parameter and good hydrogenThe United States Government has rights in this invention under Contract No. DE-AC02-83CH10093 between the United States Department of Energy and the Solar Energy Research Institute, a Division of the Midwest Research Institute.

Abstract: Process for thermal cracking of residual hydrocarbon oils by(1) feeding the oil and a synthesis gas to a thermal cracking zone, the gas having a temperature sufficiently high to maintain the temperature in the cracking zone by direct heat exchange at 420.degree.-645.degree. C.;(2) separating the cracked products into (a) a gas, (b) at least one distillate fraction and (c) a cracked residue;(3) separating the cracked residue into a heavy hydrocarbon oil poor in asphaltenes and a heavy hydrocarbon oil rich in asphaltenes;(4) gasifying the oil rich in asphaltenes in the presence of oxygen and steam to produce synthesis gas; and(5) recycling synthesis gas from step 4 as feed to step 1.

Abstract: Lubricants of improved characteristics are produced by carrying out a solvent extraction to remove aromatic components after solvent or catalytic dewaxing. Aromatic extraction solvents such as phenol, furfural or N-methyl pyrrolidone may be used. The process is particularly useful with wax-derived lubricants produced by the hydroisomerization of a petroleum wax which has then been dewaxed.

Abstract: A process for the production of hydrogen-enriched hydrocarbonaceous products which process comprises: (a) converting a heavy, asphaltene-containing hydrocarbonaceous residual oil, wherein at least 80% of the residual oil boils above 650.degree. F. (343.degree. C.), in the presence of hydrogen and a particulate catalyst at residual oil conversion conditions in a reaction zone to produce a liquid effluent stream comprising particulate catalyst and normally liquid hydrocarbonaceous compounds; (b) contacting at least a portion of the liquid effluent stream from step (a) with water and a hydrocarbonaceous solvent comprising at least one aromatic hydrocarbon; and (c) gravitationally separating the resulting admixture from step (b) into a solvent phase comprising the normally liquid hydrocarbonaceous compounds and essentially free of solids, and an aqueous phase comprising essentially all of the particulate catalyst.

Abstract: Method of producing a baseoil having a reduced coking tendency by removing precursors from the baseoil. Baseoil having reduced coking tendencies which comprises a substantially no coking precursors therein.

Abstract: I disclose a single stage, multilayered catalyst system capable of hydrodehazing and hydrofinishing a solvent dewaxed lube oil base stock. In the first layer, I catalytically dewax the solvent dewaxed stock. In the second layer, I hydrofinish the catalytically dewaxed stock. My invention also relates to a process for hydrodewaxing and hydrofinishing a solvent dewaxed lube oil base stock.

Abstract: Disclosed are methods for upgrading lube oil base stocks comprising the steps of hydrocracking such materials, preferably under relatively moderate conditions, and subsequently separating the hydrocracked materials to produce in an aromatic rich extract stream and an aromatics lean raffinate stream. The separation step is preferably achieved by solvent extraction of at least a portion of the hydrocracked material. The stream comprising the aromatic rich extract is then catalytically cracked under fluidized conditions to produce gasoline and other distillates. The aromatics lean raffinate stream is further processed by dewaxing and/or the like to produce relatively high volume metric yields of low viscosity lube oil having improved viscosity-temperature characteristics.

Abstract: The severity of a visbreaking operation is increased by treating product to remove a heavier phase in an amount of less than 15 weight percent and recycling treated product.

Abstract: The severity of a visbreaking operation is increased by treating product to remove a heavier phase in an amount of less than 15 weight percent and provide a remaining product having a Shell Hot Filtration number of less than 0.25.

Abstract: A process for producing a lubricant base oil with low pour point and high aromaticity from a feedstock oil which is either a distillate fraction boiling at 250.degree. C. or above that is obtained from a paraffin base or mixed base crude or a deasphalted oil obtained from a vacuum distillation residual oil of said crude, and process comprising:(a) the step of bringing said feedstock oil into contact with a hydrofining catalyst in the presence of hydrogen and recovering a hydrofined oil;(b) the step of dewaxing said hydrofined oil and recovering the dewaxed oil;(c) the step of subjecting said dewaxed oil to extraction with a solvent having selective affinity for aromatic hydrocarbons so as to separate the feed into the raffinate portion and the extract portion, and removing the solvent from said extract portion to obtain an extract oil; and(d) the step of treating said extract oil by means of contact with a solid adsorbent or sulfuric acid.

Abstract: An integrated refining scheme for hydroprocessing high boiling fractions such as gas oil and catalytically cracked cycle oils to produce premium quality distillates, especially jet fuels and naphthas suitable for reforming into high octane gasoline. In addition, unconverted, high boiling fractions suitable for processing by conventional refining techniques into high quality, low pour point lube base stocks are obtained. The integrated hydroprocessing comprises a first stage hydrocracking step employing an aromatic selective hydrocracking catalyst based on a large pore size acidic component such as amorphous alumina or silica alumina or a large pore size zeolite such as zeolite X or zeolite Y. The hydrocracking may be operated either in a naphtha directing mode under conditions of moderate to high severity or under conditions of low to moderate severity to produce a relatively higher proportion of product boiling in the middle distillate range.

Abstract: A process for upgrading diesel oil comprising the steps of:(1) reacting the diesel oil with a nitrogenous treating agent;(2) contacting the diesel oil from step (1) above with(a) a primary solvent selected from the group consisting of organic solvents having a dipole moment of about 1.

Abstract: A process for separating finely divided solid particles from a hydroprocessing liquid product which comprises treating a heavy hydrocarbon feed having an asphaltene content of at least 1 wt. % so as to obtain an unstable product characterized by heavy molecular weight molecules which promote the agglomeration of said finely divided solid particles and thereafter feeding said unstable product to a precipitating zone provided with a centrifugal decanter for precipitating the agglomerated solid particles and said heavy molecular weight molecules in said precipitating zone wherein at least 80 wt. % of the finely divided solid particles is recovered.

Abstract: A process for the conversion of residual asphaltene-containing hydrocarbonaceous charge stock to selectively produce large quantities of high quality middle distillate while minimizing hydrogen consumption.

Abstract: A catalytic hydrocracking process which comprises (a) introducing a reduced crude into a fractionation zone to produce a vacuum gas oil stream having a propensity to form polynuclear aromatic compounds in a hydrocracking zone and a slop wax stream; (b) contacting the vacuum gas oil stream in a hydrocracking zone with added hydrogen and a metal promoted hydrocracking catalyst at elevated temperature and pressure sufficient to gain a substantial conversion to lower boiling products; (c) partially condensing the hydrocarbon effluent from the hydrocracking zone and separating the same into a low boiling hydrocarbon product stream and an unconverted hydrocarbon stream boiling above about 650.degree. F. (343.degree. C.

Abstract: Multi-step synergistic process for converting waxy-containing hydrocarbon feedstocks to lube oil stocks having targeted pour points is disclosed. The waxy feed is first catalytically partially dewaxed with the catalyst having the structure of ZSM-5, and then the partially dewaxed oil is subjected to solvent dewaxing to reach a targeted pour point. Pretreating the crude prior to catalytic dewaxing process such as by deasphalting and aromatic removal is also disclosed. In an alternative process, the waxy-containing hydrocarbon feed is subjected to the steps of solvent dewaxing, catalytic dewaxing, and solvent dewaxing.

Abstract: The present invention is drawn to a process for the production of anode grade coke from a hydrocarbon feed characterized by high levels of sulfurs and metals. The hydrocarbon feed is hydrocracked in a hydrocracking reactor so as to produce an overhead effluent which is fed to a hot separator wherein a light hydrocarbon stream and a slurry hydrocracked product are produced. The hydrocracked product is fed to a separator and mixed with a solvent wherein the solids are separated out from the hydrocracked residual so as to produce a clean hydrocracked residual which is fed to a coking drum and coked so as to leave a mass of green anode grade coke.

Abstract: The instant invention discloses a method of removing heterocyclic basic nitrogen compounds from petroleum oils which comprises first enhancing the concentration of the heterocyclic basic nitrogen compounds in a portion of the petroleum oil and then extracting the enhanced portion of the heterocyclic basic nitrogen compounds with a two phase system having an aliphatic carboxylic acid as the extracting agent. In the hydrotreating embodiment of this invention a portion of all of the nitrogen compounds are converted to heterocyclic basic nitrogen compounds and thereby more feasibly extracted. In the distillation embodiment of this invention the nitrogen compounds are actually concentrated and thereby result in a more feasible extraction with the aliphatic carboxylic acid.

Abstract: Hydrocracking and separating process for upgrading unconverted residuals so as to increase liquid yields while at the same time decrease fouling of the hydrocracking reactor upon recycling of the upgraded residual to the hydrocracker. The unconverted residual from the hydrocracking unit is treated in a separation stage with a light hydrocarbon solvent so as to remove the polynuclear hydrocarbons from the residual prior to recycling.

Abstract: A process is disclosed for converting a heavy hydrocarbon oil feedstock to produce a high yield of lower-boiling hydrocarbons, wherein a residuum fraction of the effluent from a hydrogen donor diluent hydrocracking reactor is deasphalted using a low-boiling solvent and at least the highest-boiling fraction of the deasphalted oil is recycled to the hydrogen diluent hydrocracking zone.

Abstract: A method for reducing the nitrogen content of shale oil is disclosed. The method comprises distilling shale oil to form a distillate containing lighter shale oil compounds and a residue containing heavier compounds. Nitrogen-containing compounds are extracted from the distillate to form a first nitrogen-lean raffinate and a first nitrogen-rich extract. Nitrogen-containing compounds are also extracted from the residue to form a second nitrogen-lean raffinate and a second nitrogen-rich extract. The second nitrogen-lean raffinate is hydro-treated to further reduce its nitrogen content.

Abstract: Heavy crudes or vacuum residues are treated in a thermal hydroconversion process in the presence of a metal catalyst from Groups IVb, Vb, VIb, VIIb and VIII of the Periodic Table of Elements and water. Fresh catalyst is introduced into the process as a soluble, metallic catalyst precursor which is then decomposed while feedstock admixed with water is preheated to a temperature of at least about 230.degree. C. but no more than about 420.degree. C.

Abstract: A process for upgrading feedstocks containing not less than about 200 ppm metals, an API gravity of less than about 20.degree., a Conradson Carbon of more than about 8%, by hydroconversion with hydrogen in the presence of a naturally occurring inorganic material as a catalyst. The invention further provides, inter alia, subsequently fractionating the hydroconverted product and solvent deasphalting the distillation bottoms and optionally hydrodesulfurizing atmospheric distillates and the mix of vacuum gas oils and deasphalted oils separately. When a heavy crude of 12.degree. API, 10% Conradson Carbon, 3.2% sulfur and 350 ppm metals is fed to this process, more than 90% (v/v) of a synthetic crude of 25.degree.API, 0.17% sulfur and only 13.8% (v/v) 950.degree. F.+ fraction may be obtained.

Abstract: A coking process is provided in which a stream of heavy oil product, which typically is recycled to the coking zone, is first subjected to solvent separation using coker naphtha as solvent to separate the heavy oil into a high Conradson carbon content product comprising a minor portion of the coker naphtha and a lower Conradson carbon content product comprising a major portion of the coker naphtha and, thereafter, recovering the lower Conradson carbon content product and recycling the high Conradson content product, including the minor portion of coker naphtha, to the coking zone.

Abstract: A coking process is provided in which a stream of heavy oil product, which typically is recycled to the coking zone, is first subjected to solvent separation using coker naphtha as solvent to separate the heavy oil into a high Conradson carbon content product comprising a minor portion of the coker naphtha and a lower Conradson carbon content product comprising a major portion of the coker naphtha and, thereafter, recycling the high Conradson content product, including the minor portion of coker naphtha, to the coking zone, and separating the lower Conradson carbon content product in the coker product fractionator.

Abstract: Process for reducing the viscosity of a highly viscous hydrocarbon charge containing 10-30% b.w. of constituents distilling above 375.degree. C., said treatment comprising hydrovisbreaking said charge to such an extent as to convert 10 to 30% of the 375.degree. C..sup.+ fraction to a 375.degree. C..sup.- fraction, fractionating the hydrovisbreaked product to separate a fraction comprising at least 90% of the constituents boiling below 375.degree. C. from a distillation residue, deasphalting said distillation residue and admixing at least a portion of the deasphalted distillation residue with at least a portion of said fraction comprising at least 90% of the constituents boiling below 375.degree. C.

Abstract: Heavy hydrocarbon oils are processed by hydrotreatment over a sepiolite supported metal catalyst, described fuller in U.S. Pat. No. 4,152,250, whereby metallic impurities are removed from the oil and its asphaltene content is decreased, and the hydrotreated oil is solvent deasphalted using a propane, butane, pentane, hexane or heptane solvent or mixtures of these to give a deasphalted oil suitable for further treatment, e.g. hydrodesulphurization, and an asphaltic residue.

Abstract: A process for high hydroconversion of heavy hydrocarbon liquid feedstocks such as petroleum residua containing at least about 50 V % material boiling above 975.degree. F. to produce lower boiling hydrocarbon liquid and gas products, wherein heavy RCR materials and metals compounds are removed in-situ from the reactor effluent liquid by solvent vapor extraction using a process-derived solvent vapor at supercritical conditions. In the process, the feedstock is catalytically hydroconverted at 780.degree.-860.degree. F. temperature, and the resulting liquid fraction is contacted with a process-derived solvent vapor fraction having a normal boiling range of 250.degree.-400.degree. F. and heated to supercritical temperature to dissolve and extract substantially all the hydrocarbon liquid fractions, and separate heavy RCR materials and the metals compounds contained therein.

Abstract: A process for upgrading heavy crude comprises the hydroconversion of asphaltenes and resins in the presence of steam and ammonia at high temperatures, followed by deasphalting to eliminate metals and remaining asphaltenes. By way of the process of the present invention, conversion of asphaltenes and resins is accomplished while at the same time insuring a low formation of gases and coke so as to obtain an end product with a high yield of distillates and low metal content. The process is particularly suitable for any type of heavy crude, for example those of the Orinoco zone, which possess a high content of asphaltenes and metals.

Abstract: A process for producing a pitch which can be utilized as a raw material for producing carbon fibers is disclosed. The process involves distilling a petroleum heavy residual oil under reduced pressure to produce a reduced pressure distillation residual oil or a reduced pressure distillate oil. The distillation residual oil is subjected to a solvent deasphaltening treatment to produce a solvent deasphaltened oil. The solvent deasphaltened oil or the reduced pressure distillate oil is subjected to solvent extraction to obtain a solvent extraction component. The solvent extraction component is thermally modified to produce the pitch. The pitch can be utilized in a melt-spinning process in order to produce carbon fibers having desirable characteristics.

Abstract: A process for upgrading a heavy viscous hydrocarbon, for example, rendering a heavy viscous crude pipelinable, includes visbreaking, distillation and solvent extraction steps. A heavy viscous hydrocarbon is fed through the visbreaker which forms a feed to the distillation step. A heavier fraction from distillation is fed to a solvent extraction unit which produces a fraction which contains resin. At least a portion of the resin containing fraction separated in the solvent extraction unit is recycled and combined with the feed which is to be subject to visbreaking so that the total yield of products, residual and gas-free, is increased. The recycled resin reduces the tendency of the asphaltenes to separate from the oil and thereby reduces the tendency to lay down coke in the visbreaker; this allows higher conversion to upgraded liquid products.

Abstract: In a method of treating heavy oil, in which a gas and a volatile oil fraction produced by thermally decomposing petroleum heavy oil are distilled off, a thermal decomposition residue withdrawn in the liquid state is brought into contact with a part of the volatile oil fraction as a solvent to extract the solven-soluble component in the thermal decomposition residue, and then an extraction residue is separated as solid particles from the solvent, an improvement is disclosed which comprises fractionating the volatile oil fraction used as the solvent into two or more sub-fractions having different boiling points from each other on condensing the volatile oil fraction in a fractionating column, and contacting the sub-fractions thus-fractionated with the thermal decomposition residue progressively from the highest boiling to the lowest boiling of the fractions to extract a solvent-soluble component.

Abstract: A process for removing asphaltenes present in cat cracker bottoms is disclosed. Basically, the process requires removal of at least a portion of the polynuclear aromatic oils present in the cat cracker bottom, for example, by vacuum stripping, whereby the asphaltenes are thereafter capable of being extracted from the so-treated cat cracker bottom. Heat soaking of the asphaltene-free cat cracker bottom results in a pitch particularly suitable for carbon artifact manufacture.

Abstract: Process for the preparation of a heavy oil with a low Ramsbottom Carbon Test (RCT) from an asphalt by (a) catalytic hydrotreatment for RCT reduction at such severity that the C.sub.4.sup.- gas producton per percentage RCT reduction is kept between defined limits, followed by (b) solvent deasphalting of the (vacuum or atmospheric) distillation residue of the hydrotreated product.

Abstract: .[.In a hydrogenation operation employing an ebullated catalytic bed, recycle is recovered from the hydrogenated product with at least 25%, by volume, of the recycle boiling above 950.degree. F. The recycle is cooled to a temperature of from 350.degree. to 600.degree. F. to separate coke precursors, prior to recycle to the hydrogenation. Higher conversion levels can be achieved by effecting recycle in such manner..]..Iadd.Disclosed is a hydrogenation process using at least one fluidized catalytic stage and a recycle material of heavy hydrogenated effluent. The heavy effluent material is cooled to a temperature within 350.degree.-600.degree. F. to separate toluene and heptane insoluble coke precursors prior to recycle. This separation may be enhanced by the use of centrifugation, filtration or a bed of particulate material (e.g. calcined coke). .Iaddend.