Description

BACKGROUND OF THE INVENTION

Field of The Invention

The present invention relates to a process for the hydro- conversion of heavy hydrocarbonaceous fractions of petroleum. In particular, it relates to a close-coupled two- stage; thermo-catalytic, catalytic -hydrotreatment process for converting petroleum heavy oils that provides improved effectiveness for high conversion and control of condensation reactions to produce stable high-quality products. Background

Increasingly, petroleum refiners find a need to make use of heavier or poorer quality crude feedstocks in their processing. As that need increases, the need also grows to process the fractions of those poorer feedstock's boiling at elevated temperatures, particularly those boiling above 540°C. High conversions to stable, quality products are desirable in order to avoid producing significant quantities of low value fuel oil. Delayed Coking, the refiner's traditional solution for converting heavy oils to liquid products, has become less attractive because of the low conversion to liquid products and the relatively low value of the coke by-product. Higher liquid conversions can be achieved with conventional ebullated bed technologies. But these technologies, even with enhancements such as solvent de-asphalting, suffer limitations due to the instability of the fuel oil product and refractive nature of the prod- ucts - making further upgrading difficult. Severe conditions are required in order to achieve high conversions which, while producing desirable lighter fractions, can also produce thermally cracked fragments and unstable asphaltenes that form mesophase masses. Unless controlled, the cracked fragments undergo condensation reactions to undesirable polycyclic molecules which tend to be difficult to process into desirable products and to form an unstable phase. Along with the mesophase masses, which constitute a highly viscous phase with a tendency to deactivate catalysts by physically blocking active sites, the polycyclic molecules can also lead to coke formation.

The key to high conversion and product quality is the management of the asphaltenes which are both in the heavy oil feed and produced at severe operating conditions. Current approaches have focused on slurry reactor technology utilizing sophisticated dispersed catalyst systems, in some cases employing molybdenum. These technologies tend to have high investment and operating costs and, in some cases, product quality remains an issue. Many of these processes also have difficulties if the metals content of the feedstock is high.

Various processes for the conversion of heavy hydrocarbo- naceous fractions, particularly, multi-stage conversion processes include those described in U.S. Pat. No.

4,761,220, Beret, et al . ; U.S. Pat. No. 4,564,439,

Kuehler, et al . ,- U.S. Pat. No. 4,330,393, Rosenthal, et al.; U.S. Pat. No. 4,422,922, Rosenthal, et al . ; U.S. Pat. No. 4,354,920, Rosenthal, et al; U.S. Pat. No. 4,391,699, Rosenthal , et al . In the following the term "reaction zone" shall be understood as a section of the process equipment in which a reaction occurs. A reaction zone according to the present disclosure, may comprise multiple physical reactors, or it may comprise only a part of a reactor. Hence,, a reaction zone shall be construed as having similar reaction conditions within the reaction zone, and reaction conditions being different from those in other reaction zones of the process, unless otherwise indicated.

In the following the term "two stage process" shall be understood as a process comprising two reaction zones. The process may be conducted in two reactors, but also in a single reactor or in more than two reactors, where several reactors operate under similar conditions, as long as the number of independent sets of process conditions is two. The definition shall also be construed to cover a process with more than two stages, as long as an essential part of the process is conducted in two sets of process conditions similar to those described in the present application.

In the following the term hydrocarbonaceous feedstock shall be understood as a feedstock dominated by hydrocarbons, but in which heteroatoms such as oxygen, nitrogen, sulphur, and metal may also be present. Such hydrocarbonaceous feedstock may include crude petroleum, topped crude petroleum, reduced crudes, petroleum residua from atmospheric or vacuum distillations, solvent deasphalted tars and oils, heavy hydrocarbonaceous liquids derived from coal, bitumen, biomass or coal tar pitches, without being limited to such materials. In the following the terms heavy hydrocarbons and heavy oils are used synonymously, indicating a hydrocarbonaceous material boiling above 540 °C. A heavy hydrocarbonaceous feedstock shall be understood as being dominated by such heavy hydrocarbons, i.e. comprising at least 30% of heavy hydrocarbons .

In the following the term close-coupled shall be. understood as the connection of two reaction zones, in a manner such that the process conditions do not include an intermediate process regime which allows undesired reactions.

Specifically the thermo-catalytic reaction zone of the present disclosure is considered close-coupled to the catalytic-hydrotreating reaction zone, if the process conditions allowing condensation reactions are minimized.

For the practical implementation of the invention it is acceptable that close-coupling is not adhered to strictly, and for this purpose the term "substantially close- coupled" is used. "Substantially close- coupled" may be construed according to the following definition; at least 90% of the fraction of the thermo-catalytic product boiling above 100°C is transferred to the catalytic- hydrotreating zone. A further narrower requirement to the close-coupling between the reaction zones, is defined by the intermediate conditions between the thermo-catalytic reaction zone and the catalytic-hydrotreating reaction zone being such that they do not promote condensation, po- lymerisation or coupling reactions between unstable species. Specifically this definition of close- coupling conditions may be further narrowed such that the intermediate residence time under a partial pressure of hydrogen below 35 atmospheres, must be less than 4.0 hr. , preferably less than 1.0 hr .

Furthermore where at least 10% of the fraction of the thermo catalytic product boiling above 100°C undergoes specific separation or purification steps such as filtration, distillation, centrifugation, solvent deasphalting, etc. the process shall specifically not be considered close-coupled, whereas simpler separation steps such as separation in a hot separator is still considered close- coupling, as they do not imply process conditions favouring condensation and/or coupling reactions of heavy free radicals and other unstable species. In the following the term dispersed material shall mean a (solid) material, being well distributed within a liquid. The term shall not be construed as specific physical or chemical relationship between the materials, other than at least a substantial part of the solid material remaining in solid phase, and a substantial part of the surface of the solid material being in contact with the liquid.

In the following the term unstable, shall be taken to include a chemically unstable constituent or a thermodynami- cally unstable phase. An unstable constituent shall be construed as any constituent having an increased propensity to undergo chemical reaction, either by decomposition or by recombination, such as condensation, with other constituents, especially unstable constituents. The unstable constituent may be a free radical, or it may be a molecule in reactive form. An unstable phase shall be construed as dissolved matter, which has a propensity to separate as solids or viscous insoluble liquid. In the following streams may be designated by the reactions they have undergone, such as hydrotreater effluent. This terminology shall only be construed as the effluent from the hydrotreatment reaction zone, and not as limited to an effluent which has been fully hydrotreated.

In the following materials may be described as solids, liquid or gaseous. Where this description is linked to a specific temperature and pressure the material is solid, liquid or gaseous respectively at this temperature. Where no temperature and pressure is specified the material is solids, liquid or gaseous respectively at 20°C and 1 atmosphere .

SUMMARY

The present invention is, in broad scope, a process for converting the portion of heavy oil feedstock boiling above 540 °C, to produce high yields of high quality products boiling below 540°C. Compared to existing processes, the products are reduced in heteroatom content, reduced in condensed molecules and are more readily processed to finished fuels. The process comprises introducing a mixture comprising heavy hydrocarbonaceous feedstock, coal and dispersed particles of active material, into a thermo-catalytic reaction zone in the presence of hydrogen and operated at elevated temperature and pressure. The mixture of feedstock, coal and dispersed particles of active material is introduced into the thermo-catalytic zone under conditions sufficient to convert a significant amount of hydrocarbons in the feedstock boiling above 540 °C to hydrocarbons boiling below 540 °C. In one embodiment, substantially all of the thermo-catalytic product, including gaseous, liquid and solid phases is passed in a substantially close-coupled manner into a catalytic-hydrotreating zone with inter- zone cooling to reduce temperature prior to the catalytic- hydrotreating. The thermo-catalytic product is contacted with hydrotreating catalysts under hydrotreating conditions, and the hydrotreater effluent from catalytic- hydrotreating reaction zone is recovered.

In another embodiment a portion of the gaseous products from the thermo-catalytic reaction zone are removed. In this embodiment, substantially all of the thermo-catalytic product is passed directly, in a close-coupled manner, into a catalytic-hydrotreating reaction zone with inter- zone cooling to reduce temperature prior to the second stage zone. As in the first embodiment, the thermo- catalytic product is contacted with hydrotreating catalysts under hydrotreating conditions, and the hydrotreater effluent from catalytic-hydrotreating reaction zone is recovered.

In its broadest form the present invention relates to a two- stage, process for converting a heavy hydrocarbona- ceous feedstock comprising the process steps:

a. forming a slurry by dispersing within said heavy hy- drocarbonaceous feedstock

i. coal particles and

ii. particles of an active material having catalytic hy- drocarbon conversion activity in the presence of hydrogen b. introducing said slurry into a thermo-catalytic stage under conditions sufficient to convert an amount of the hydrocarbons in said feedstock boiling above 540°C and an amount of the coal particles to hydrocarbons boiling below 540°C forming a thermo-catalytic product and

c. passing at least a portion of the, thermo-catalytic product into a catalytic-hydrotreating reaction stage sub- stantially close coupled to said thermo-catalytic stage, d. contacting said thermo-catalytic product under hy- drotreating conditions with a material active in hydro- processing and providing a hydrotreater effluent

e. recovering the hydrotreater effluent from said cata- lytic-hydrotreating reaction zone, with the associated benefit that thermo-catalytic product remains reactive in the catalytic-hydrotreating zone, as free radicals are not undergoing ^■ condensation reactions . In a further embodiment at least 90% of the thermo- catalytic product boiling above 100°C is passed into the catalytic-hydrotreating zone, such that the amount of thermo-catalytic product which may undergo condensation reactions is kept at a minimum.

In a further embodiment at least 10% of the fraction boiling below 20°C of the thermo-catalytic product is removed before passing the thermo-catalytic product to the catalytic-hydrotreating zone, with the associated benefit of reducing the volume of feed to the catalytic-hydrotreating reaction zone, improving the downstream gas purity and improving the hydrodynamics if the downstream hydrotreating reactor (s) is configured as a fixed bed upflow reactor. In a further embodiment the dispersed active material comprises oxides, hydroxides or sulfides of metals chosen from the Groups VIb, VIlb and Vlllb metals with the asso- ciated benefit of being a material especially active in the conversion of the hydrocarbons.

In a further embodiment wherein the dispersed active mate- rial comprises one or more of a synthetic catalyst, a waste product and a naturally occurring material, with the respective associated benefits of being well defined, or ^' being cheap and simple to obtain. In a further embodiment the dispersed active material comprises one or both of a naturally occurring iron oxide and a naturally occurring iron hydroxide mineral such as limo- nite, red mud and iron ore with the associated benefit of having a high activity while being especially cheap and simple to obtain.

In a further embodiment the temperature of said thermo- catalytic zone is maintained within a range of 400 °C to 480°C, and more preferred 430°C to 470°C, in which the re- activity is very high, while the products still are dominated by valuable C4+ hydrocarbons.

In a further embodiment the products from the catalytic- hydrotreating zone are separated into gaseous, liquid and a liquid/solid bottom fractions and wherein a portion of the liquid and/or liquid/solid fraction bottoms is recycled back to the feed system, with the associated benefit of providing conversion of the recycled heavy bottoms. In a further embodiment the products from the catalytic- hydrotreating zone are separated into gaseous and liquid/solid bottom fractions and wherein a portion of a gaseous fraction containing hydrogen is recycled to the catalytic-hydrotreating reaction zone or the thermo- catalytic reaction zone with the associated benefit of efficient use of hydrogen in the process. In a further embodiment temperature of the catalytic- hydrotreating zone is between 320°C to 430°C, with the associated benefit of providing optimal and specific conditions for hydrotreatment . In a further embodiment the amount of heavy hydrocarbona- ceous feedstock converted to hydrocarbons boiling below 540°C is at least 50 percent, preferably at least 75 percent, with the associated benefit of providing an high yield of valuable product.

In a further embodiment said heavy hydrocarbonaceous feedstock is selected from the group consisting of crude petroleum, topped crude petroleum, reduced crudes, petroleum residua from atmospheric or vacuum distillations, solvent deasphalted tars and oils, heavy hydrocarbonaceous liquids derived from coal, bitumen, biomass, or coal tar pitches, with the associated benefit of said feedstocks being low cost raw materials. In a further embodiment said heavy hydrocarbonaceous feedstock is co-processed with one or more feedstocks taken from the group of Vacuum Gas Oil, Coker Gas Oil, Fluid Catalytic Cracking Cycle Oil, and oil derived from biomass with the associated benefit of simpler handling by the presence of less viscous materials.

In a further embodiment the concentration of coal dispersed in the feed to the thermo-catalytic zone is between 0.5 and 40 percent, preferably 0.5 to 20 percent and even more preferably 3 to 10 percent by weight, with the associated effect of being a sufficient amount for solubiliz- ing the heavy feedstock and for binding metals from the feedstock, while being easy to handle.

In a further embodiment the amount of dispersed active material in the slurry fed to the thermo-catalytic zone is from about 0.1 to 5 percent by weight, with the associated effect of being sufficient for catalyzing the thermo- catalytic cracking reactions, while avoiding problems with pumping the slurry, and avoiding excessive material costs.

In a further embodiment the residence time of the material in the thermo-catalytic reaction zone is from about 0.5 to 3 hours, with the associated effect of matching the requirements for a complete thermo-catalytic cracking reaction. In a further embodiment the residence time of material in the catalytic-hydrotreating reaction zone is from about 0.3 to 4 hours, with the associated effect of matching the requirements for a complete hydrotreatment reaction. In a further embodiment the supported catalyst in said catalytic-hydrotreating zone is maintained within the catalytic-hydrotreatment reaction zone in a fixed bed, with the associated benefit of a simple stable reactor, or ■ in an ebullated or moving bed(s) with the associated bene- fit of being robust towards the presence of particles in the thermo-catalytic product, respectively. In a further embodiment the process is maintained at a hydrogen partial pressure from about 35 atmospheres to 300 atmospheres, with the associated benefit of the thermo- catalytic products being stabilised, and the hydrotreat- ment reaction being optimised.

In a further embodiment the hydrocarbonaceous feedstock comprises metal contaminants including one or more metals taken from the group consisting of nickel, vanadium, and iron wherein the concentration of said metals in the liquid phase are reduced by at least 80% in the thermo- catalytic stage.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic flow diagram of one embodiment of the process of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is a process for hydroconversion of heavy oil feedstocks that effectively controls asphaltene condensation by utilization of a combination of dispersed coal, dispersed particles of active material, and a two- stage close-coupled thermo-catalytic reactor/catalytic- hydrotreating reactor configuration. It converts heavy hy- drocarbonaceous feed-stocks, a significant portion of which boils above 540 °C, to high yields of high quality products boiling below 540 °C.

The process, in one embodiment, is a two-stage, close- coupled process, the first stage of which encompasses a thermo-catalytic reaction zone, wherein the feedstock is substantially converted to lower boiling products. The product of the thermo-catalytic zone is cooled somewhat and passed, either without substantial loss of hydrogen partial pressure or with only short term loss of hydrogen partial pressure, into a catalytic-hydrotreating zone, where the thermo-catalytic product is hydrotreated to pro- duce a hydrotreater effluent, comprising hydrotreated products suitable for further treatment into transportation fuels and other products. In the thermo-catalytic zone, the dispersed particles of active material catalyses the hydrogenation of thermally cracked fragments and tem- porarily stabilizes them thus preventing condensation reactions. The dispersed particles of active material also hydrogenates coal liquids, which coal liquids in a non- catalytic process also act to hydrogenate thermally cracked fragments by donating hydrogen to them. The coal liquids also act to solubilize asphaltenes and asphaltenes precursors and inhibit the formation of mesophase masses, which may deactivate the catalyst by blocking the access to the active catalytic sites. The close-coupling of the catalytic-hydrotreating zone plays a key role in stabiliz- ing remaining thermally cracked fragments from the thermo- catalytic reaction zone, hydrogenating products, removing heteroatoms and effecting some further molecular weight reduction. The unconverted coal and coal ash sequester the metals in the feedstock in the thermo-catalytic zone which results in substantial reduction of metals fouling of the supported hydrotreating catalyst in the catalytic- hydrotreating zone, thus providing increased activity and lifetime of the hydrotreating catalyst. Thermo-catalytic cracking tends to produce unstable products. This can lead to both the fouling of downstream equipment and the production of poor quality products. Substantially close-coupling the lower temperature cata- lytic-hydrotreating zone after the thermo-catalytic zone assures the prompt saturation and thus chemical stabilisation of unstable molecules that were created in the thermo-catalytic reaction zone. In contrast to conven- tional processing, which places separations steps after the thermo-catalytic zone, and does not directly pass the liquids and liquids/solids from the thermo-catalytic zone to a catalytic-hydrotreating zone, this prompt stabilization significantly reduces the polymerization of unstable molecules to form undesirable asphaltenes . Thus, the zones are substantially "close-coupled", but due to practical consideration strict close-coupling may be refrained from, as long as the conditions where polymerisation, could occur are kept to a minimum.

The conditions in the process lines between the thermo- catalytic zone and the catalytic-hydrotreating zone are maintained such that the hydrogen partial pressure is maintained above 35 atmospheres. In a close-coupled system also, there is no separation of solids from liquids as the thermo-catalytic product passes from one zone to the other, and there is no more cooling and reheating than necessary. However, it is preferred to cool the thermo-catalytic product by passing it through a cooling zone prior to the second stage. This cooling does not affect the close- coupled nature of the system. The cooling zone will typically contain a heat exchanger or similar means, whereby the thermo catalytic product is cooled to a temperature between 320°C to 430°C in order to reach a temperature suitable for hydrotreating without excessive fouling of the hydrotreating catalyst in the catalytic-hydrotreater. Some cooling may also be effected by the addition of a fresh, cold, hydrogen-rich stream.

Feedstocks finding particular use within the scope of this invention are heavy hydrocarbonaceous feedstocks, at least 30 volume percent, preferably 50 volume percent of which boils above 540 °C. Examples of typical feedstocks include crude petroleum, topped crude petroleum, reduced crudes, petroleum residua from atmospheric or vacuum distilla- tions, solvent deasphalted tars and oils, and heavy hydro- carbonaceous liquids including residua derived from coal, bitumen, biomass, or coal tar pitches. Herein, these constituents are referred to as "heavy oil". Other feedstocks such as vacuum gas oils, coker gas oils, oils derived from biomass, and FCC cycle oils may also be co-processed with these heavy oils.

The process of the present disclosure may be more fully understood by reference to Figure 1 that illustrates one embodiment of the present disclosure. Heavy oil feedstock (hydrocarbonaceous feedstocks, a significant portion of which boils above 540°C) enters the process by line 5. Some portion of the feed is mixed (mixer 10) with finely divided coal and particles of active material from line 8 to disperse the coal and particles of active material in the heavy feedstock. Hydrogen is introduced via conduit 62 and constitutes fresh hydrogen via conduit 6, recycled gases via conduit 52 or mixtures thereof. It is a preferred feature of the present disclosure that the added coal and active material be highly dispersed. The added coal and dispersed particles of active material are mixed with the feedstock in mixing zone 10 to form a slurry, preferably a dispersion or uniform distribution of parti- cles within the feed, which is introduced into a thermo- catalytic reaction zone 20 via conduit 18 together with heavy oil feed via conduit 58. Coal is added in the mixture in a concentration relative to the feedstock from 0.5 to 40 percent by weight, preferably 0.5 to 20 percent by weight and more preferably from about 3 to 10 percent by weight. About 3 to 10 percent coal addition will be suitable for most feeds and operations, balancing the need for the presence of coal, with practical considerations for handling of the feed. High volatile bituminous coals are preferred due to their high hydroaromatic content and ease of liquefaction, but coals of other rank may be suitable. The coal particles must be finely divided, having a maximum diameter of about 40 mesh U.S. sieve series, prefera- bly smaller than 100 mesh and more preferably under 10 microns .

Prior to introduction into the thermo-catalytic reaction zone, the feedstock slurry and hydrogen-containing streams are heated to provide an operating temperature of between 400°C to 480°C, preferably 430°C to 470°C, in the zone. This heating may be done to the entire feed to the zone or may be accomplished by segregated heating of the various components or combinations of the components of the total feed (for example, feed-solids slurry, feed-gas mixture, feed only, gas only) .

The heated combined oil, hydrogen-rich gas, coal and active material pass by line 15 to an upflow thermo- catalytic reaction zone 20 and out by conduit 25 to cooling means 30 and by conduit 35 to hydrotreating-reaction zone 40. Hydrogen-rich gas may be added by line 28. In addition to cooling the thermo-catalytic product stream. this gas addition will result in higher hydrogen partial pressure and lead to more efficient usage of the hydrotreater catalyst. The short route of products from reactor 20 to reactor 40 helps to minimize asphaltene and mesophase production. However, in some embodiments, it may be desirable to remove a portion of the gas that is present in the thermo-catalytic zone. Since small quantities of water and light gases are produced in the thermo- catalytic zone, the catalyst in the catalytic- hydrotreating zone may be subjected to a slightly lower hydrogen partial pressure than if these materials were absent. Thus, in this embodiment thermo-catalytic product from reactor 20 passes by line 25 to the hot separator 42. Preferably, the entire bottoms stream from separator 42 is passed to the - catalytic-hydrotreating zone. Furthermore, this inter- stage removal of the carbon monoxide and other oxygen-containing gases may reduce the hydrogen consumption in the catalytic-hydrotreating stage. The removal of all or a portion of the gas from the thermo-catalytic product might also be done to provide improved hydrodynamics in the downstream catalytic-hydrotreating zone. In any case, the removal of gas is to be done in a manner that does not cause significant residence time in the absence of hydrogen for the solids-containing liquids from the thermo-catalytic zone to the catalytic-hydrotreating zone where the process conditions are more favorable for the stabilization of heavy hydrocarbon molecules. The hydrogen-rich stream (conduit 51) may be treated and recycled to the thermo-catalytic or catalytic-hydrotreating zones.

Hydrotreater effluent from zone 40 passes by conduit 45 to separator 50 where the gas phase is separated from the liquid/solids phase. The gas phase (conduit 53) may be treated and a hydrogen rich stream may be recycled back to the thermo-catalytic and/or the catalytic-hydrotreating zone. The liquid/solids bottoms from the separator 50 passes by conduit 55 to atmospheric distillation column 60 where gases are removed by conduit 66 and liquid fractions are removed as schematically shown by conduit 64. In operation several streams of different boiling range products may be separately removed. The bottoms stream (conduit 65) is further distilled in vacuum column 70 to sepa- rate a vacuum distillate product (conduit 72) from a solids-containing vacuum bottoms stream (conduit 75) . In some cases it may be desirable to recycle all or a portion of these streams back to the feed system via conduits 76 and/or 78.

Other reaction conditions in the thermo-catalytic zone include residence time of from 0.5 to 3 hours, preferably 0.5 to 1.5 hours; a hydrogen partial pressure in the range of 35 to 300 atmospheres, preferably 100 to 200 atmos- pheres, and more preferably 100 to 175 atmospheres; and a hydrogen gas rate of 350 to 3000 liters per liter of feed mixture and preferably 400 to 2000 liters per liter of feed mixture. Under these conditions, a significant amount of the hydrocarbons in the feedstock boiling above 540 °C. is converted to hydrocarbons boiling below 540 °C. In the present disclosure, the percentage of hydrocarbons boiling above 540 °C. converted to those boiling below 540 °C are at least 50 percent, more preferably 75 percent and most preferably more than 90 percent.

The dispersed particles of active material is present in the mixture in a concentration relative to the feedstock of from about 0.1 to 5 percent by weight, preferably 0.5 to 1 percent by weight. Suitable dispersed particles of active material would be the oxides or sulfides of metals selected from Groups VIb, Vllb and Vlllb. It is preferred that the dispersed particles of active material not be supported on a base material. The dispersed particles of active material may be either synthetic or naturally occurring minerals such as limonite, red mud and iron ore. The particles of active material should also be finely divided, having a maximum diameter of about 40 mesh U.S. sieve series, and preferably smaller than 100 mesh, and most preferably less than 10 microns. In one embodiment, naturally occurring catalyst are preferred. Such catalysts are effective, relatively cheap and widely available in sufficient quantities. Finely ground limonite, a naturally occurring iron oxide/hydroxide mineral is especially preferred.

The catalytic-hydrotreating reaction zone may be a fixed, ebullating, or moving bed all of which are well known to those skilled in the art.

In the catalytic-hydrotreating reaction zone, predominantly hydrogenation occurs which further stabilizes unstable molecules from the thermo-catalytic zone and also removes heteroatoms such that the product will also have been substantially desulfurized, denitrified, and deoxy- genated. Some cracking may also occur simultaneously, such that some higher-molecular-weight compounds are converted to lower-molecular-weight compounds.

Catalyst used in the catalytic-hydrotreating zone may be any of the well-known, commercially available hydroproc- essing catalysts. A suitable catalyst for use in this re- action zone comprises a hydrogenation component supported on a suitable refractory base. Suitable bases include silica, alumina, or a composite of two or more refractory oxides. Suitable hydrogenation components are selected from Group VI-B metals, Group VIII metals and their oxides, sulfides or mixture thereof. Particularly useful are cobalt-molybdenum, nickel-molybdenum, or nickel-tungsten .

In the catalytic-hydrotreating zone, it is preferred to maintain the temperature below 430°C, preferably in the range of 320°C to 430°C, and more preferably between 340 °C to 420°C to prevent catalyst fouling. Other hydrocatalytic conditions include a hydrogen partial pressure from 35 atmospheres to 300 atmospheres, preferably 100 to 200 atmos- pheres, and more preferably 100 to 175 atmospheres; a hydrogen flow rate of 300 to 1500 N liters per liter of feed mixture, preferably 350 to 1000 N liters per liter of feed mixture; and a residence time in the range of 0.3 to 4 hours, preferably 0.5 to 3 hours.

Typical heavy hydrocarbonaceous feedstocks of the kind that find application in the process of the present disclosure often contain undesirable amounts of metallic contaminants. Unless removed, these contaminants can result in deactivation of the second-stage hydrotreating catalyst, and/or plugging of the catalyst bed resulting in an increase in the pressure drop in the bed of supported hydrotreating catalyst. The present disclosure is well suited for the processing of feeds that are high in metal- lie contaminants because most of these contaminants are removed from the feed and deposited on un-dissolved coal and ash. If a relatively low amount of coal is used or if the coal is insufficient in un-dissolved coal and/or ash, to assist in metals removal additional coal ash may be added, preferably together with the coal and the active material. The present disclosure is also particularly well suited for feeds that are derived from crudes that are high in residuum content, especially those that are also high in contaminants, since high quality products can be obtained from these lower cost crudes.

The process of the present disclosure produces liquid products, a significant portion of which boils below 540°C and which are suitable for processing to transportation fuels. The normally liquid products, that is, all of the product fractions boiling above C ₄ , have a specific gravity in the range of naturally occurring petroleum stocks. Ad- ditionally, relative to the feed, the total product will have at least 80 percent of sulfur removed and at least 30 percent of nitrogen removed. Products boiling in the transportation fuel range may require additional upgrading prior to use as a transportation fuel.

The process is operated at conditions and with sufficient severity to convert at least fifty (50) percent of the heavy oil feedstock boiling above 540°C to products boiling below 540°C, and preferably at least seventy-five (75) percent conversion and more preferably to at least ninety (90) percent conversion.

Examples

The process has been studied further according to the following examples . Common for the examples studied the conditions of the thermo-catalytic reaction was a temperature of 450°C, total pressure of, and a hydrogen partial pressure of 160 atmospheres and a residence time of 0.35 hr. The catalytic hydrotreatment reaction was studied in the presence of a nickel molybdenum catalyst, a temperature of 370°C, a residence time of 2.38 hr and an unchanged inlet hydrogen partial pressure of 160 atmospheres. In a first example, according to the prior art, 1 kg/hr of a heavy feedstock, comprising 10% asphaltenes was combined with 1% (10 g/hr) limonite and 5% (50 g/hr) coal, and directed to a first thermo-catalytic reactor, operating at 450°C, with a residence time of 0.35 hr. The thermo- catalytic product was directed to a separation process in which unconverted material and limonite was separated from lighter fractions in a hot flash separator with a residence time of 0.32 hr, following which the lighter fractions were hydrotreated in a hydrotreater operating at 370°C, with a residence time of 2.38 hr. The yields according to this example are listed in Table I.

In a second example, according to an embodiment of the present disclosure, 1 kg/hr of a heavy feedstock, compris- ing 10% asphaltenes was combined with 1% (10 g/hr) limonite and 5% (50 g/hr) coal, and directed to the first thermo-catalytic reactor. All of the thermo-catalytic product was directed to be hydrotreated in a hydrotreater operating at 370°C, with a residence time of 2.38 hr. The yields according to this example are listed in Table II.

A comparison between examples 1 and 2 shows that the yield of distillate is 13% higher according to the present dis- closure, and that in example 1, according to the prior art, 100 g/hr of the feed is withdrawn in the separator bottom fraction, of which 5 g/hr is asphaltene, and a further 30 g/hr of the feed remains as asphaltenes in the product .

In this specification and drawing, the present disclosure has been described with reference to specific embodiments. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification is, accordingly, to be regarded in an illustrative rather than a restrictive sense. Therefore, the scope of the invention should be limited only by the appended claims.

Table I

Feed Thermo Separator Hydrotreater (kg/h Catalytic Bottom Out (kg/hr) r) Reactor (kg/hr)

out

(kg/hr)

Resid 0.900 0.300 0.050 0.070

Coal 0.050 0.005 0.002 0.004

Asphal- 0.100 0.043 0.052 0.030 tene

Distil0.000 0.779 0.000 0.946 late

Table II

Feed Thermo Catalytic Hydrotreater Out

(kg/hr) Reactor out (kg/hr)

(kg/hr)

Resid 0.900 0.300 0.083

Coal 0.050 0.005 0.005

Asphaltene 0.100 0.043 0.004

Distillate 0.000 0.779 1.062