Abstract: The present invention relates to a method for joint production of low octane gasoline and high octane gasoline. In the process of oil or light oil rectification, the extraction points of the distillates therein are finely divided, and the temperature ranges for extraction of fractions are narrowed down. Each of the low and high octane components having a high content in the range from C6-C12 (which may be extended to C5-C14 where necessary) is then separately extracted. After that, low octane components are combined into compression ignition low octane gasoline products, while high octane components are combined into high octane gasoline products. The remaining fractions are respectively added as supplementing agents into the low octane gasoline products or high octane gasoline products dependent on their octane ratings. Low octane gasoline is used in compression ignition gasoline engines, while high octane gasoline is used in spark ignition gasoline engines.

Abstract: Heavy gas oil components, coking process recycle, and heavier hydrocarbons in the delayed coking process are cracked in the coking vessel by injecting a catalytic additive into the vapors above the gas/liquid-solid interface in the coke drum during the coking cycle. The additive comprises cracking catalyst(s) and quenching agent(s), alone or in combination with seeding agent(s), excess reactant(s), carrier fluid(s), or any combination thereof to modify reaction kinetics to preferentially crack these components. The quenching effect of the additive can be effectively used to condense the highest boiling point compounds of the traditional recycle onto the catalyst(s), thereby focusing the catalyst exposure to these target reactants. Exemplary embodiments of the present invention can also provide methods to (1) reduce coke production, (2) reduce fuel gas production, and (3) increase liquids production.

Abstract: A hydrocarbon feed is passed to a first zone of a vaporization unit to separate a first vapor stream and a first liquid stream. The first liquid stream is passed to a second zone of the vaporization unit and contacted with a counter-current steam to produce a second vapor stream and a second liquid stream. The first vapor stream and the second vapor stream are cracked in the radiant section of the steam cracker to produce a cracked effluent. The second liquid stream is catalytically cracked to produce a cracked product. The cracked product is distilled to produce an overhead stream, a light cycle oil, and a heavy cycle oil. The light cycle oil is reacted with hydrogen in the presence of a catalyst to produce a hydrotreated light cycle oil. The hydrotreated light cycle oil and the overhead stream are fed to the vaporization unit.

Abstract: An integrated thermal and catalytic process for improving the yield of middle distillate from heavy petroleum oil feeds comprises cracking the heavy portion (345° C.+) of the feed in a thermal conversion zone, followed by hydrotreating the thermally cracked product and the lighter portion of the feed and then separating the hydrotreated product into a bottoms fraction which is passed to a catalytic cracking step.

Abstract: Methods and systems for upgrading hydrocarbon material, including bituminous material such as tar sands. A hydrocarbon material and a cracking material can be injected into separate injection ports of a nozzle reactor to produce a hydrocarbon product. The hydrocarbon product can be injected directly into a coker so that heavy hydrocarbon compounds can be upgraded into lighter hydrocarbon compounds, or the hydrocarbon product can first be injected into a separation vessel to separate hydrocarbons having higher boiling point temperature from hydrocarbons having lower boiling point temperature. The hydrocarbons having higher boiling point temperature can then be injected into a coker.

Abstract: The present invention describes a process for the production of gasoline in a fluid catalytic cracking unit having at least one principal reactor operating using feeds with a low Conradson Carbon and a high hydrogen content, said process comprising recycling a coking cut either to a side chamber branching off the stripper or within the stripper itself by means of a tubular vessel within said stripper.

Abstract: Undesirable gas oil components are selectively cracked or coked in a coking vessel by injecting an additive into the vapors of traditional coking processes in the coking vessel prior to fractionation. The additive contains catalyst(s), seeding agent(s), excess reactant(s), quenching agent(s), carrier(s), or any combination thereof to modify reaction kinetics to preferentially crack or coke these undesirable components that typically have a high propensity to coke. Exemplary embodiments of the present invention also provide methods to control the (1) coke crystalline structure and (2) the quantity and quality of volatile combustible materials (VCMs) in the resulting coke. That is, by varying the quantity and quality of the catalyst, seeding agent, and/or excess reactant the process may affect the quality and quantity of the coke produced, particularly with respect to the crystalline structure (or morphology) of the coke and the quantity & quality of the VCMs in the coke.

Abstract: A reactor process added to a coking process to modify the quantity or yield of a coking process product and/or modify certain characteristics or properties of coking process products.

Abstract: The present invention is directed to the upgrading of heavy hydrocarbon feedstock that utilizes a short residence pyrolytic reactor operating under conditions that cracks and chemically upgrades the feedstock. The method for upgrading a heavy hydrocarbon feedstock comprises introducing a particulate heat carrier into an upflow reactor, introducing the heavy hydrocarbon feedstock into the upflow reactor at a location above that of the particulate heat carrier so that a loading ratio of the particulate heat carrier to feedstock is from about 15:1 to about 200:1, allowing the heavy hydrocarbon feedstock to interact with the heat carrier with a residence time of less than about 1 second, to produce a product stream, separating the product stream from the particulate heat carrier, regenerating the particulate heat carrier, and collecting a gaseous and liquid product from the product stream.

Abstract: This invention relates to a process for the selective conversion of vacuum gas oil. The vacuum gas oil is treated in a two step process. The first is thermal conversion and the second is catalytic cracking of the products of thermal conversion. The product slate can be varied by changing the conditions in the thermal and catalytic cracking steps as well as by changing the catalyst in the cracking step. The combined products from thermal and catalytic cracking are separated in a divided wall fractionator.

Abstract: The present invention relates to a process for the selective conversion of hydrocarbon feed having a Conradson Carbon Residue content of 0 to 6 wt %, based on the hydrocarbon feed. The hydrocarbon feed is treated in a two-step process. The first is thermal conversion and the second is catalytic cracking of the products of the thermal conversion. The present invention results in a process for increasing the distillate production from a hydrocarbon feedstream for a fluid catalytic cracking unit. The resulting product slate from the present invention can be further varied by changing the conditions in the thermal and catalytic cracking steps as well as by changing the catalyst in the cracking step.

Abstract: A process is disclosed for contacting feed with mixed catalyst in a secondary reactor that is incorporated into an FCC reactor. The mixed catalyst used in the secondary reactor is regenerated catalyst from a regenerator that regenerates spent catalyst from an FCC reactor that is mixed with spent catalyst from either the FCC reactor or the secondary reactor. The mixing of spent and regenerated catalyst reduces the catalyst temperature and tempers catalyst activity to inhibit both thermal and catalytic cracking reactions.

Abstract: The invention is to provide a catalyst excellent in product producibility and selectivity, and in coking degradation resistance and regeneration degradation resistance, which is for production of ethylene and propylene through catalytic conversion from a hydrocarbon material. The invention relates to a method for producing ethylene and propylene through catalytic conversion from an olefin, by contacting a hydrocarbon material with a zeolite-containing shaped catalyst satisfying the following requirements (1) to (6), in a reactor: (1) the zeolite is an intermediate pore-size zeolite having a pore size of from 5 to 6.5 angstroms, (2) the zeolite does not substantially contain a proton, (3) the zeolite contains at least one metal selected from the group consisting of metals belonging to the Group IB of the Periodic Table, (4) the zeolite-containing shaped catalyst comprises silica as a binder, (5) the zeolite-containing shaped catalyst has a side-crush strength of at least 2.

Abstract: The invention is to provide a catalyst for long-term, high-yield and stable production of ethylene and propylene in an efficient and simple method of catalytic conversion from a hydrocarbon material. The invention relates to a method for producing ethylene and propylene by contacting a hydrocarbon material that contains an olefin having from 4 to 12 carbon atoms in an amount of at least 20% by weight, with a zeolite-containing shaped catalyst satisfying the following requirements (1) to (4), in a reactor for catalytic conversion of that olefin: (1) the zeolite is an intermediate pore-size zeolite having a pore size of from 5 to 6.5 angstroms, (2) the zeolite does not substantially contain a proton, (3) the zeolite contains at least one metal selected from the group consisting of metals belonging to the Group IB of the Periodic Table, (4) the zeolite has a silica/alumina molar ratio (SiO2/Al2O3 molar ratio) of from 800 to 2,000.

Abstract: A process and apparatus are provided for upgrading steam cracked tars. The invention also relates to a steam cracking process and apparatus for reducing the yields of tars produced from steam cracking while increasing yields of higher value products, heating, in the presence of steam, cooled steam cracker tar containing asphaltenes, to a temperature, e.g., above about 300° C., which is sufficient to convert at least a portion of the steam cracked tar to lower boiling molecules. The resulting heat and steam-treated tar can be separated into gas oil, fuel oil and tar streams.

Abstract: The main distinctive feature of the method lies in the fact that the hydrocarbon material is affected through primary and principal excitation by means of electromagnetic vibrations. The primary influence upon the hydrocarbon material is carried out prior to its feeding for thermal cracking, while the, principal influence is fulfilled in the rectifying column. For the method to be implemented, the primary excitation source in the installation is realized in a form of an electromagnetic oscillator, and the rectifying column is realized with possibility of resonance excitation provided, being the main exciter of the hydrocarbon material. The invention makes it possible to increase the percentage of output of lighter fractions, as well as to raise the quality of processing of raw materials.

Abstract: A process for increasing ethylene yield in a cracked hydrocarbon is provided. A hydrocarbon feed stream comprising at least 90% by weight of one or more C4-C10 hydrocarbons can be heated to provide an effluent stream comprising at least 10% by weight propylene. The effluent stream can be selectively separated to provide a first stream comprising heavy naphtha, light cycle oil, slurry oil, or any combination thereof and a second stream comprising one or more C4-C10 hydrocarbons. The second stream can be treated to remove oxygenates, acid gases, water, or any combination thereof to provide a third stream comprising the one or more C4-C10 hydrocarbons. The third stream can be selectively separated to provide a product stream comprising at least 30% by weight propylene. At least a portion of the product stream can be recycled to the hydrocarbon feed stream to increase ethylene yield in the effluent stream.

Abstract: A process for efficiently and stably producing ethylene and propylene which comprises bringing a hydrocarbon feedstock comprising at least one C4-12 olefin into contact with a zeolite-containing catalyst to obtain a reaction mixture containing ethylene and propylene, separating the reaction mixture into a fraction comprising ingredients ranging from hydrogen to C3 hydrocarbons and a fraction comprising C4 and higher hydrocarbons, and recycling the C4 and higher hydrocarbons as they are to a reactor.

Abstract: A method for thermally cracking a feed composed of whole crude oil and/or natural gas condensate using a partitioned vaporizer to gasify the feed before cracking same.

Abstract: A process for the fluid catalytic cracking of mixed hydrocarbon feeds from different sources is described, such as feeds A and B of different crackability, the process being especially directed to obtaining light fractions such as LPG and comprising injecting feed A in the base of the riser reactive section and feed B, of lower crackability, at a height between 10% and 80% of the riser, with feed B comprising between 5% and 50% of the total processed feed. The process requires that the feeds present differences in the contaminant content, improved dispersion of feeds A and B and feed B injection temperature same or higher than that of feed A.

Abstract: A process is disclosed for producing needle coke from heavy atmospheric distillation residues having sulfur no more than 0.7 wt %, which process involves the steps of heating the feedstock to a temperature in the range of 440 to 520° C. for thermal cracking in a soaking column under pressure in the range of 1 to 10 kg/cm2 to separate the easily cokable material, separating the cracked products in a quench column and a distillation column and then subjecting the hydrocarbon fraction from the bottom of the quench column and a hydrocarbon fraction having a boiling point in the range of 380 to 480° C. from the distillation column and/or any other suitable heavier hydrocarbon streams in a definite ratio depending on certain characteristic parameters to thermal cracking in a second soaking column at a temperature of 460 to 540° C.

Abstract: A process for the conversion of a hydrocarbon feedstock to produce olefins, aromatic compounds and ultra low sulfur diesel wherein the hydrocarbon feedstock is reacted in a fluid catalytic cracking (FCC) zone to produce olefins and light cycle oil. The effluent from the FCC is preferably separated to produce a stream comprising ethylene and propylene, a stream comprising higher boiling olefins and light cycle oil (LCO). The stream containing the higher boiling olefins is cracked to provide additional ethylene and propylene. The LCO is selectively hydrocracked to produce aromatic compounds and ultra low sulfur diesel.

Abstract: A device for the fluidized bed cracking of a hydrocarbon charge using two reaction chambers linked together by a cooling particles transferrer, a fractionating column and conduits to supply the hydrocarbonated effluents from each of the two chambers to the fractionating column. The fractionating column has, internally, at least two different areas: a first partitioned fractionating area in the form of two compartments, each of which communicates with a second common fractionating area. The conduits for the supply of effluents from the first and the second reaction chamber terminate, respectively, in the first and second compartment of the partitioned fractionating area. A recycler and an injector are provided for recycling and injecting into one of the reaction chambers of at least one cut drawn off from the partitioned fractionating compartment of the effluents of the other reaction chamber.

Abstract: The present invention relates to a process for the conversion of hydrocarbon streams with 95% true boiling point less than 400° C. to very high yield of liquefied petroleum gas in the range of 45-65 wt % of feed and high octane gasoline, the said process comprises catalytic cracking of the hydrocarbons using a solid fluidizable catalyst comprising a medium pore crystalline alumino-silicates with or without Y-zeolite, non crystalline acidic materials or combinations thereof in a fluidized dense bed reactor operating at a temperature range of 400 to 550° C., pressure range of 2 to 20 kg/cm2 (g) and weight hourly space velocity in range of 0.1 to 20 hour?1, wherein the said dense bed reactor is in flow communication to a catalyst stripper and a regenerator for continuous regeneration of the coked catalyst in presence of air and or oxygen containing gases, the catalyst being continuously circulated between the reactor-regenerator system.

Abstract: The present invention relates to a catalytic cracking process and a device used in the process in particular, the present invention provides a catalytic cracking process, which comprises which comprises: 1) catalytic cracking a feedstock in the first riser for less than about 1.5 second and sending the resultant stream into the first separating device,; 2) catalytic cracking the recycle oil obtained from the first separating device in the second riser for less than about 1.

Abstract: Disclosed is an apparatus and process for controlling space velocity in a fluidized catalytic conversion reactor. The catalyst flux rate can be adjusted during the process of the reaction to adjust the space velocity and maintain a fast fluidized flow regime therein. The set parameter in the reactor may be pressure drop which is proportional to catalyst density.

Abstract: According to this invention, there is provided a process and apparatus for catalytic cracking of various petroleum based heavy feed stocks in the presence of solid zeolite catalyst and high pore size acidic components for selective bottom cracking and mixtures thereof, in multiple riser type continuously circulating fluidized bed reactors operated at different severities to produce high yield of middle distillates, in the range of 50–65 wt % of fresh feed.

Abstract: A process and apparatus are disclosed contacting hydrocarbon feed with catalyst in a reactor vessel under conditions more vigorous than bubbling bed conditions and preferably fast fluidized flow conditions. The vigorous conditions assure thorough mixing of catalyst and feed to suppress formation of dry gas and the promotion of hydrogen transfer reactions.

Abstract: A process and apparatus is disclosed for contacting feed with mixed catalyst in a secondary reactor that is incorporated into an FCC reactor. The mixed catalyst used in the secondary reactor is regenerated catalyst from a regenerator that regenerates spent catalyst from an FCC reactor that is mixed with spent catalyst from either the FCC reactor or the secondary reactor. The mixing of spent and regenerated catalyst reduces the catalyst temperature and tempers catalyst activity to inhibit both thermal and catalytic cracking reactions.

Abstract: The invention relates to a process for converting cycle oils produced in catalytic cracking reactions into olefin and naphtha. More particularly, the invention relates to a process for hydroprocessing a catalytically cracked light cycle oil, and then re-cracking it in an upstream zone of the primary FCC riser reactor.

Abstract: The invention relates to a process for converting cycle oils produced in catalytic cracking reactions into light olefin and naphtha. More particularly, the invention relates to a process for hydroprocessing a catalytically cracked light cycle oil in order to form a hydroprocessed cycle oil containing a significant amount of tetralins. The hydroprocessed cycle oil is then re-cracked in an upstream zone of the primary FCC riser reactor.

Abstract: The present invention relates to a catalytic cracking process and a device used in the process in particular, the present invention provides a catalytic cracking process, which comprises which comprises:

Abstract: A process for cracking, in a fluidized bed, a hydrocarbon charge wherein the cooling particles, which may optionally also be catalytic particles, circulate in two successive reaction chambers (1; 16), in each of which they are brought into contact with at least one cut of hydrocarbons, and the reaction effluents from each of the chambers are directed towards one and the same fractionating unit. The effluents from each of the reaction chambers (1; 16) are fractionated in part separately in one and the same partially partitioned fractionating unit, and at least one cut (12) obtained by separately fractionating the effluents from one of the two reaction chambers (1; 16) is, as a whole or in part, reinjected into the other chamber.

Abstract: Disclosed is a method for producing ethylene and propylene from a hydrocarbon feedstock by catalytic conversion, which comprises contacting, in a reactor, a hydrocarbon feedstock comprising 20% by weight or more, based on the weight of the hydrocarbon feedstock, of at least one C4-C12 olefin with a zeolite-containing catalyst, wherein the zeolite in the zeolite-containing catalyst satisfies the following requirements: (1) the zeolite is an intermediate pore size zeolite having a pore size of from 5 to 6.5 Å, (2) the zeolite contains substantially no proton, (3) the zeolite contains at least one metal selected from the group consisting of metals belonging to Group IB of the Periodic Table, and (4) the zeolite has an SiO2/Al2O3 molar ratio of from 200 to 5,000, to effect a catalytic conversion reaction of the hydrocarbon feedstock, thereby obtaining a reaction mixture containing ethylene and propylene; and separating the ethylene and propylene from the reaction mixture.

Abstract: Disclosed is a catalytic cracking process that includes more than one catalytic cracking reaction step. The process integrates catalytic cracking steps with hydroprocessing in order to maximize olefins production, distillate quality and octane level of the overall cracked product. Preferably, one hydroprocessing step is included between the cat cracking reaction steps, and a portion of the hydroprocessed products, i.e., a naphtha and mid distillate fraction, is combined with cracked product for further separation and hydroprocessing. It is also preferred that the first catalytic cracking reaction step be a short contact time reaction step.

Abstract: A process for upgrading petroleum residua to more valuable products by visbreaking or otherwise thermally cracking a petroleum residuum to produce a thermally cracked bottoms stream, vacuum distilling at least a portion of the thermally cracked bottoms stream to produce a vacuum distilled thermally cracked pitch, blending a portion of the pitch with a hydrocarbon residuum that is not a vacuum distilled thermally cracked pitch to produce a delayed coker feed component, producing a delayed coker heater charge having a recycle ratio, by weight, of less than about 1.27:1, and introducing the coker heater charge into a delayed coker.

Abstract: A multi-step process for converting non-aromatic hydrocarbons (preferably a gasoline-type hydrocarbon mixture) to lower olefins (preferably, ethylene and propylene) and aromatic hydrocarbons (preferably benzene, toluene and xylene) comprises, in sequence, a first reaction step, a first separation step, a second reaction step, and a second separation step, wherein the reaction severity of the first reaction step is lower than in the second reaction step so as to maximize olefins and aromatics yields.

Abstract: Disclosed is a catalytic cracking process which includes more than one catalytic cracking reaction step. The process integrates a hydroprocessing process step between the catalytic cracking reaction steps in order to maximize olefins production, mid-distillate quality and naphtha octane level in the cracked products. Preferably, a first cracked hydrocarbon product is obtained from a first cracking stage and separated into a mid-distillate and gas oil containing fraction having an initial boiling point of at least 300.degree. F., the distillate and gas oil containing fraction is hydroprocessed, and a naphtha fraction and a gas oil containing bottoms fraction of the hydroprocessed material are cracked in a second cracking stage.

Abstract: Disclosed is a catalytic cracking process which includes more than one catalytic cracking reaction step. The process integrates a hydroprocessing step between the catalytic cracking reaction steps in order to maximize olefins production, distillate quality and octane level of the overall cracked product. Preferably, the hydroprocessing step is included between the reaction stages, and a portion of the hydroprocessed products, i.e., a naphtha and mid distillate fraction, is combined with cracked product for further separation and hydroprocessing. It is also preferred that the first catalytic cracking reaction step be a short contact time reaction step.

Abstract: A process for the production of diesel fuel with a high cetane number at a low cloud point, which involves hydrocracking highly aromatic fractions obtained from catalytic cracking operations. The fraction of hydrocracker effluent which boils between about 400.degree. F. (205.degree. C.) and 1000.degree. F. (538.degree. C.) is subsequently catalytically dewaxed in order to obtain a cloud point of no more than 41.degree. F. (5.degree. C.). The hydrocracker effluent fraction is preferably recycled to the hydrocracking step prior to dewaxing.

Abstract: Disclosed is a catalytic cracking process which includes more than one catalytic cracking reaction step. The process integrates a hydroprocessing step between the catalytic cracking reaction steps in order to maximize olefins production, distillate quality and octane level of the overall cracked product. Preferably, the hydroprocessing step is included between the reaction stages, and a portion of the hydroprocessed products, i.e., a naphtha and mid distillate fraction, is combined with cracked product for further separation and hydroprocessing. It is also preferred that the first catalytic cracking reaction step be a short contact time reaction step.

Abstract: The invention relates to a process for catalytic cracking and the associated apparatus in which the cracking reaction takes place in two substantially vertical and successive reaction zones, the loads being introduced into the first zone where it circulates from the top downwards, then at least a part of the product obtained is introduced into a second reaction zone in which it circulates in an ascending fashion. A supplementary hydrocarbonated phase is advantageously introduced into the product entering the second zone. The invention applies particularly to heavy loads, with a U-shaped apparatus.

Abstract: A process for multi-stage catalytic cracking is disclosed. A first stage cracks a first feed at atmospheric to 100 psig over a shape selective zeolite to convert from 10 to 90%, by volume, to lighter products rich in iso-compounds which may be used to make ethers. A second feed, which may include 700.degree. F.+ liquid from the selective cracking reaction, is cracked in a catalytic cracking (FCC) unit. Preferably all or some of the products from the shape selective cracking reactor are fractionated in the FCC main column.

Abstract: The present invention provides a process for hydrodelayed thermal cracking in combination with hydrostripping, which comprises feeding crude oil from a surge tank to a crude oil stripper via a feed line; separating the crude oil into a lighter fraction and a heavier fraction in the crude oil stripper; subjecting the lighter fraction to hydrodesulfurization; feeding the heavier fraction from the crude oil stripper to a first storage tank; hydrothermally cracking the heavier fraction for at least 10 minutes under a hydrogen pressure in the first storage tank; introducing a bottom residue of the first storage tank into a second storage tank or the feed line, and subjecting a cracked and vaporized fraction of the first storage tank to hydrodesulfurization; hydrothermally cracking the residue introduced into the second storage tank under a higher hydrogen pressure than the hydrogen pressure of the first storage tank; subjecting a portion of a bottom residue of the second storage tank to hydrodemetallization, hydro

Abstract: A fluid catalytic cracking (FCC) process and apparatus which employs relatively more elutriatable catalyst particles comprising intermediate pore zeolite, particularly ZSM-5, and relatively less elutriatable catalyst particles comprising large pore zeolite, preferably zeolite Y. The process and apparatus employ a first stripping vessel which also separates a more elutriatable first portion of catalyst from a less elutriatable second portion of catalyst. The more elutriatable first portion passes to a second stripping vessel, and subsequently recycles to a fluid catalytic cracking reactor riser. The second portion of less elutriatable catalyst passes from the first stripping vessel to a fluid catalytic cracking regenerator vessel and, after being regenerated, recycles to the reactor riser. The more elutriatable first portion contains a higher ratio of intermediate pore catalyst particles to large pore catalyst particles than does the second portion.

Abstract: The invention describes a process for producing light products, such as engine and diesel fuels, and fuel oils for conventional use by thermal conversion of heavy metal- and sulfur-rich-crude oil residues. Thermal cracking of the residues is done by mild cracking in several stages, where the residue remaining after separation of the conversion products of the preceding stage is fed to the respective subsequent stage.

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 novel FCC method and apparatus, wherein a fresh hydrocarbon feed of relatively poor crackability is fed to one riser of a two riser system. The spent catalyst from the other of the two risers is fed to the inlet of the first riser to produce relatively mild cracking conditions. Improved total gasoline plus distillate yields are achieved. The novel two riser system facilitates heat balancing of the system.

Abstract: Hydrocarbon feedstocks, especially those high in Ramsbottom carbon, are vaporized by contact with a relatively inactive coked cracking catalyst, separating the resulting intermediate into a high and low boiling fraction, and cracking the high boiling fraction in a fluid catalytic cracker containing active cracking catalyst.

Abstract: A heavy hydrocarbon oil comprising constituents boiling above 1050.degree. F. is upgraded by a combination visbreaking or hydrovisbreaking and hydrorefining process in which at least a portion of the hydrorefined bottoms fraction is recycled to the visbreaking zone. The hydrorefining zone is operated at conditions to convert at least a portion of the 1050.degree. F..sup.+ constituents to lower boiling hydrocarbons.