Method and system for mixing a catalyst precursor into heavy oil using a high-boiling hydrocarbon diluent

Abstract

A system and method for mixing a catalyst precursor into heavy oil, forming a diluted precursor mixture using a high-boiling hydrocarbon diluent, mixing the diluted precursor mixture with a heavy oil feedstock to form an adjusted feedstock, subsequently heating the adjusted feedstock to decompose the precursor, and forming dispersed metal sulfide catalyst particles in-situ. Since the high-boiling hydrocarbon diluent is typically at a temperature above the decomposition temperature of the catalyst precursor, it is first fed to a cooler to lower its temperature and avoid premature decomposition of the catalyst precursor. The high-boiling hydrocarbon diluent may include a portion of the heavy oil feedstock, a portion of the adjusted feedstock, a vacuum tower bottom product, or other high-boiling hydrocarbon materials having a boiling point above 524 °C. A portion of the diluent may optionally include a medium-boiling hydrocarbon material having a boiling point below 524 °C.

Description

Technical Field

[0001] 1. Background Art of the Present Invention

[0001] The present invention relates to a method and system for mixing a catalyst precursor into a heavy oil feedstock using a high-boiling hydrocarbon as a diluent prior to hydrotreating.

Background Art

[0002] 2. Related Art

[0002] Converting heavy oil into useful end products involves extensive processing such as reducing the boiling point of the heavy oil, increasing the hydrogen-to-carbon ratio, and removing impurities such as metals, sulfur, nitrogen, and coke precursors. Examples of hydrocracking processes for upgrading atmospheric column bottoms and / or vacuum column bottoms using conventional heterogeneous catalysts include fixed-bed hydrotreating, fluidized-bed hydrotreating, and moving-bed hydrotreating. Hydrocracking can also be performed using a homogeneous catalyst in a slurry-phase reactor.

[0003]

[0003] The demand for more efficiently utilizing low-quality heavy oil feedstocks and obtaining valuable fuels therefrom is increasing. Low-quality feedstocks are characterized by containing a relatively large amount of hydrocarbons boiling above nominally 524 °C (975 °F). They also contain relatively high concentrations of asphaltenes, sulfur, nitrogen, and / or metals. The high-boiling fractions derived from these low-quality feedstocks typically have high molecular weights (often exhibiting higher densities and viscosities), and / or low hydrogen / carbon ratios, which are associated with the presence of high concentrations of undesirable components including asphaltenes and carbon residues. Asphaltenes and carbon residues contribute to the formation of coke and deposits, making the processing difficult and often causing fouling of conventional catalysts and hydroconversion units.

[0004]

[0004] Low-quality heavy oil feedstocks contain higher concentrations of asphaltenes, carbon residues, sulfur, nitrogen, and metals. Examples include heavy crude oil, oil sand bitumen, and residual oils remaining from conventional refining processes. Residuum (or "resid") may refer to atmospheric column bottoms and vacuum column bottoms. Atmospheric column bottoms can have a boiling point of at least 343 °C (650 °F), but the cut point can vary between refineries and is understood to be as high as 380 °C (716 °F). Vacuum column bottoms (also known as "resid pitch" or "vacuum residue") can have a boiling point of at least 524 °C (975 °F), but the cut point can vary between refineries and is understood to be as high as 538 °C (1000 °F), or even 565 °C (1050 °F).

[0005]

[0005] For comparison, Alberta light crude contains approximately 9 volume % vacuum residue, while Lloydminster heavy oil contains approximately 41 volume % vacuum residue, Cold Lake bitumen contains approximately 50 volume % vacuum residue, and Athabasca bitumen contains approximately 51 volume % vacuum residue. As a further comparison, relatively light oils such as Dansk Blend from the North Sea region contain only approximately 15% vacuum residue, while lower-quality European oils such as Urals contain more than 30% vacuum residue, and oils such as Arab Medium are even higher, containing approximately 40% vacuum residue.

[0006]

[0006] In a given fluidized bed system, the production rate of the converted product is often limited by fouling. When attempts are made to increase the production of the converted product beyond a certain practical limit, the rate of fouling of the mixer, heat exchanger, strainer, and other processing equipment becomes too rapid, requiring more frequent shutdowns for maintenance and cleaning. Typically, refinery operators relate the observed rate of fouling of the equipment to the measured value of precipitate formation and reach an operating sedimentation limit, beyond which the refinery will avoid operating the fluidized bed hydrocracker. Thus, precipitate formation and equipment fouling impose a practical upper limit on the conversion and the production rate of the converted product. Such problems are exacerbated when using lower quality heavy oil feedstocks.

[0007]

[0007] Fluidized bed reactors utilizing a dual catalyst system composed of a heterogeneous catalyst and a dispersed (e.g., metal sulfide) catalyst have been used to reduce equipment fouling and / or increase the production rate of the converted product. The success or failure of the dual catalyst system depends on several variables, including the particle size of the dispersed catalyst, which is a result of how it is formed. In the case of a metal sulfide catalyst formed from a catalyst precursor, the resulting catalyst size and activity are primarily based on how well it is dispersed in the heavy oil before pyrolyzing to form the active catalyst. If the catalyst precursor is not properly dispersed in the heavy oil before pyrolysis, the resulting metal sulfide catalyst particles formed in the heavy oil feedstock may have low catalytic activity and actually cause more equipment fouling, negating its effectiveness as a catalyst.

[0008]

[0008] When using a dispersed catalyst to enhance the performance of a fluidized bed hydrogenation treatment system, it is preferred to first prepare a diluted precursor mixture and then mix the diluted precursor mixture with the heavy oil feedstock. This is prepared by mixing a hydrocarbon diluent with a catalyst precursor, and the catalyst precursor is selected based on availability, cost, compatibility of addition to the hydrogenation treatment process, and the ability to solubilize the precursor. Such a diluted precursor mixture disperses more readily in the bulk of the heavy oil feedstock compared to directly mixing the precursor with the heavy oil feedstock. It can be difficult to properly mix the catalyst precursor by simply adding it to the heavy oil feedstock, and such a simple addition can result in a poorly mixed material that is likely to give undesirably large or aggregated catalyst particles when the dispersed catalyst is subsequently activated by heating the feedstock mixture.

[0009]

[0009] To form a diluted precursor mixture and then mix it into the heavy oil feedstock, low-boiling and medium-boiling hydrocarbons may be used as diluents for the catalyst precursor. Materials such as startup diesel fuel, vacuum gas oil, atmospheric gas oil, decanted oil, cycle oil, etc. are suitable medium-boiling diluents. These materials have a nominal boiling point in the range of 200 °C to 524 °C and have good solubility for the dispersed catalyst precursor. Further, these materials are typically processed and / or stored in a temperature range that renders them suitable for use as diluents without further treatment. This is because it is advantageous to use the diluent at a temperature below the decomposition temperature of the catalyst precursor so that the precursor is completely dissolved and dispersed before significant decomposition of the precursor and activation of the dispersed metal sulfide catalyst particles occur.

[0010] However, in some hydrocracking facilities, this type of material is either unavailable or disadvantageous for use for this purpose. For example, the hydrocracking unit may operate at or near the upper limit of the processing capacity of the heavy feedstock. Adding a mid-boiling diluent to the process replaces part of the heavy feedstock, thereby reducing the effective capacity of the heavy feedstock processing system below the required level. Another reason is that available mid-boiling materials may be the converted products of the hydrocracking process and thus may have sufficient value for commercial sale, or in the manufacture of salable products, they are actually too costly to enable their use as diluents. Potential mid-boiling materials may be required as raw materials or intermediates for other processing systems in a complex commercial facility, making their use as diluents unavailable.

[0011] Alternatively, using a mid-boiling hydrocarbon diluent may cause processing problems. For example, the unit feedstock may already contain a limited amount of mid-boiling material. Mid-boiling components in the unit feed can contribute to precipitate formation, which is exacerbated by adding additional amounts of mid-boiling hydrocarbons to the feedstock via the diluent precursor mixture. There may be compatibility issues between the heavy oil feedstock and readily available mid-boiling diluent sources, which can result in sedimentation and more severe fouling in the hydrotreating unit. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0012]

[0012] A method and system are disclosed herein that are particularly configured to form an adjusted feedstock as a preparation for hydrotreating heavy oil using one or more hydrotreating reactors by mixing a catalyst precursor with a high-boiling hydrocarbon diluent to form a catalyst precursor mixture and then mixing the catalyst precursor mixture with a heavy oil feedstock. When the adjusted feedstock is heated, the catalyst precursor can be pyrolyzed to form dispersed metal sulfide catalyst particles, which have high catalytic activity and promote beneficial upgrading reactions when hydrotreating heavy oil.

[0013]

[0013] The methods and systems of the present disclosure provide for the effective use of dispersed catalysts in a fluidized-bed hydroconversion system when middle-boiling materials are not available or are disadvantageous as diluents for the preparation of the diluted precursor mixture.

[0014]

[0014] The high-boiling hydrocarbon diluent can include one or more high-boiling hydrocarbons such as vacuum residues, vacuum tower bottoms, other heavy oil feedstocks, deasphalted heavy oils, and / or sidestreams of adjusted heavy oil feedstocks formed using the methods and systems of the present disclosure. Typically, the high-boiling hydrocarbon has an ASTM boiling point above 524 °C. The high-boiling hydrocarbon diluent can optionally contain or be mixed with middle-boiling hydrocarbons such as startup diesel, vacuum gas oil, atmospheric gas, decanted oil, cycle oil, or other hydrocarbons having an ASTM boiling point in the range of about 200 °C to 524 °C.

[0015]

[0015] In some embodiments, the hydrocarbon diluent consists entirely of high-boiling materials. In alternative embodiments, a portion of the hydrocarbon diluent may include medium-boiling materials such that the diluent is a mixture of high-boiling and medium-boiling hydrocarbons. The high-boiling hydrocarbon diluent preferably contains at least 25 volume %, at least 50 volume %, at least 70 volume %, at least 80 volume %, at least 90 volume %, or at least 95 volume % of one or more high-boiling hydrocarbons, and less than 75 volume %, less than 50 volume %, less than 30 volume %, less than 20 volume %, less than 10 volume %, less than 5 volume % of one or more medium-boiling hydrocarbons. In some embodiments, the high-boiling hydrocarbon diluent consists essentially of one or more high-boiling hydrocarbons and essentially omits one or more medium-boiling hydrocarbons.

[0016]

[0016] Consistent with the foregoing, the high-boiling hydrocarbon diluent contains one or more high-boiling hydrocarbons having a boiling point of at least 524 °C, and optionally one or more medium-boiling hydrocarbons, such that the diluent has a nominal boiling point of at least 350 °C, preferably at least 400 °C, more preferably at least 450 °C, most preferably at least 500 °C, for example, at least 524 °C. The cut point used as the definition of "vacuum residue" or "vacuum tower bottom" can vary between refineries, and it should be noted that some refineries use a cut point of 524 °C, others use a cut point of 540 °C, and still others use a cut point of 565 °C. If the vacuum residue has a cut point higher than 524 °C, it may be advantageous to include medium-boiling hydrocarbons that reduce the viscosity of the high-boiling hydrocarbon diluent used to form the catalyst precursor mixture.

[0017]

[0017] Preferred catalyst precursors are oil-soluble, have a decomposition temperature, and decompose when exceeding it. Therefore, it is advantageous for the hydrocarbon diluent to have a temperature lower than the decomposition temperature of the catalyst precursor to prevent premature decomposition and the formation of aggregated catalyst particles with low activity. Unfortunately, available high-boiling hydrocarbons are typically maintained at a relatively high temperature of up to 300 °C mainly to reduce the viscosity of the high-boiling materials so that they can be easily pumped and processed.

[0018]

[0018] The temperature at which high-boiling hydrocarbons are typically maintained is generally too high to use these materials as diluents for catalyst precursors. When high-boiling hydrocarbons are directly mixed with the catalyst precursor at their normal storage temperature(s), they cause premature decomposition of the precursor, induce aggregation of the dispersed catalyst in the catalyst precursor mixture, and significantly reduce the performance of the dispersed catalyst when used to hydrotreat heavy oil feedstocks.

[0019]

[0019] To address this problem, the methods and systems of the present disclosure utilize a cooler (e.g., a heat exchanger) to control the temperature of the high-boiling hydrocarbon diluent. The selection and control of this temperature are important because it must be high enough to enable the high-boiling hydrocarbon to have a sufficiently low viscosity and be mixable with the catalyst precursor in a fluid state, but not so high as to avoid premature decomposition and undesirable aggregation of the dispersed catalyst particles. In some embodiments, the high-boiling hydrocarbon diluent is preferably cooled to a temperature in the range of about 75 °C to about 150 °C, more preferably in the range of about 75 °C to about 125 °C, and most preferably in the range of about 75 °C to about 95 °C.

[0020] The process of cooling the high-boiling hydrocarbon diluent may include adding one or more middle-boiling hydrocarbons to the high-boiling material. The middle-boiling hydrocarbons are often stored or maintained at a temperature of less than 150 °C, preferably less than 125 °C, more preferably less than 95 °C. Thereby, the cooling process may include a step of cooling the high-boiling hydrocarbon diluent using a cooler, and a part of the cooling may be the result of mixing in the middle-boiling hydrocarbons which are already at a lower temperature.

[0021]

[0021] The high-boiling hydrocarbon diluent can be used in an amount in the range of 0.1% to 10% by volume, or 0.5% to 5% by volume of the total feedstock going to the hydrotreating unit. The sources of high-boiling diluents (such as heavy oil feedstock, adjusted heavy oil feedstock, vacuum residue, deasphalted heavy oil, and vacuum tower bottoms) can be individually used at 0.1% to 10%, or 0.5% to 5% of the total heavy oil feedstock, or they can be used in any combination that together amounts to 0.1% to 10% or 0.5% to 5% of the total heavy oil feedstock. Such high-boiling hydrocarbon diluent sources can optionally be individually combined with one or more middle-boiling hydrocarbons, or with one or more heavy boiling diluent sources in any combination that together amounts to 0.1% to 10% or 0.5% to 5% of the total heavy oil feedstock.

[0022]

[0022] An exemplary method of mixing a catalyst precursor into a heavy oil feedstock is (1) preparing a catalyst precursor having a decomposition temperature, (2) preparing a high-boiling hydrocarbon diluent composed of one or more high-boiling hydrocarbons and optionally one or more middle-boiling hydrocarbons, initially having a temperature above the decomposition temperature of the catalyst precursor, (3) cooling the high-boiling hydrocarbon diluent to a temperature lower than the decomposition temperature of the catalyst precursor, (4) mixing the catalyst precursor with the high-boiling hydrocarbon diluent to form a diluted precursor mixture, and (5) mixing the diluted precursor mixture with the heavy oil feedstock to form an adjusted feedstock.

[0023]

[0023] An exemplary system for mixing a catalyst precursor into a heavy oil feedstock includes (1) a catalyst precursor supply line that provides a catalyst precursor at a temperature lower than the decomposition temperature of the catalyst precursor, (2) at least one diluent supply line that provides a high-boiling hydrocarbon diluent composed of one or more high-boiling hydrocarbons and optionally one or more medium-boiling hydrocarbons at an initial temperature above the decomposition temperature of the catalyst precursor, (3) at least one cooler configured to cool the high-boiling hydrocarbon diluent to a temperature lower than the decomposition temperature of the catalyst precursor, (4) at least one premixer configured to receive the catalyst precursor and blend it with the high-boiling hydrocarbon diluent to form a pre-diluent mixture, and (5) at least one mixer configured to mix the pre-diluent mixture with the heavy oil feedstock to form a conditioned feedstock.

[0024]

[0024] In some embodiments, cooling of the high-boiling hydrocarbon diluent is accomplished solely by one or more coolers, such as one or more heat exchangers. In other embodiments, cooling of the high-boiling hydrocarbon diluent includes the addition of a medium-boiling hydrocarbon that already has a temperature lower than the decomposition temperature of the catalyst precursor.

[0025]

[0025] The method and system may include a plurality of different mixers and / or different types of mixers, such as static in-line mixers, high-shear mixers, surge tank(s) with pump-around, and pumps used to supply the heavy oil feedstock to a hydrotreating reactor.

[0026]

[0026] In some embodiments, a portion of the heavy oil feedstock can be used as a diluent to form the pre-diluent mixture. When used as a diluent, the heavy oil feedstock advantageously passes through a heat exchanger to lower its temperature before being mixed with the catalyst precursor.

[0027]

[0027] In other embodiments, a portion of the adjusted feedstock can be used as a diluent to form a diluted precursor mixture. When used as a diluent, the adjusted feedstock advantageously has its temperature reduced before passing through a heat exchanger and being mixed with the catalyst precursor.

[0028]

[0028] In still other embodiments, the vacuum tower bottom product can be used as a diluent to form a diluted precursor mixture. When used as a diluent, the vacuum tower bottom product advantageously has its temperature reduced before passing through a heat exchanger and being mixed with the catalyst precursor.

[0029]

[0029] In yet other embodiments, the deasphalted heavy oil can be used as a diluent to form a diluted precursor mixture. When used as a diluent, the deasphalted heavy oil advantageously has its temperature reduced before passing through a heat exchanger and being mixed with the catalyst precursor.

[0030]

[0030] The catalyst precursor is preferably oil-soluble and has a decomposition temperature in the range of about 100 °C (212 °F) to about 350 °C (662 °F), or in the range of about 150 °C (302 °F) to about 300 °C (572 °F), or in the range of about 175 °C (347 °F) to about 250 °C (482 °F). Examples of catalyst precursors include organometallic complexes or compounds, more specifically, oil-soluble compounds or complexes of transition metals and organic acids that have a decomposition temperature or range high enough to avoid substantial decomposition when mixed with a heavy oil feedstock under suitable mixing conditions. When mixing the catalyst precursor with a hydrocarbon oil diluent, it is advantageous to maintain the diluent below the temperature at which significant decomposition of the catalyst precursor occurs. One skilled in the art can select a mixing temperature profile that results in intimate mixing of the selected precursor composition without substantial decomposition prior to the in-situ formation of the dispersed metal sulfide catalyst particles.

[0031]

[0031] The adjusted feedstock can be passed through a heater to decompose at least a portion of the catalyst precursor and form in-situ dispersed metal sulfide catalyst particles in the heavy oil feedstock before entering the hydrotreating reactor. For example, the adjusted feedstock can be removed from a surge tank (e.g., a heated surge tank) and passed through a heater. Alternatively or in addition, at least a portion of the adjusted feedstock can be heated within the hydrotreating reactor itself to decompose at least a portion of the catalyst precursor and form in-situ dispersed metal sulfide catalyst particles in the heavy oil feedstock. It has been found that preheating the adjusted feedstock upstream of the hydrotreating reactor provides a more active dispersed catalyst.

[0032]

[0032] In some embodiments, the dispersed metal sulfide catalyst particles have a size less than 1 μm, or less than about 500 nm, or less than about 250 nm, or less than about 100 nm, or less than about 50 nm, or less than about 25 nm, or less than about 10 nm, or less than about 5 nm.

[0033]

[0033] In some embodiments, the heavy oil feedstock containing the in-situ formed dispersed metal sulfide catalyst can be hydrotreated under hydrotreating conditions, where the dispersed metal sulfide catalyst promotes beneficial hydrogenation and other upgrading reactions in the presence of heat and hydrogen. The hydrotreating can be carried out by one or more hydrotreating reactors selected from slurry-phase reactors, ebullated-bed reactors, and fixed-bed reactors.

[0034]

[0034] For example, the hydrotreating of heavy oil can be carried out using one or more ebullated-bed reactors that utilize a dispersed metal sulfide catalyst in combination with a heterogeneous ebullated-bed catalyst to produce upgraded heavy oil. Instead of or in addition to one or more ebullated-bed reactors, the hydrotreating of heavy oil can be carried out using one or more slurry-phase reactors that utilize a dispersed metal sulfide catalyst as the sole catalyst or in combination with a conventional slurry catalyst, and / or one or more fixed-bed reactors that utilize a dispersed metal sulfide catalyst in combination with a heterogeneous fixed-bed catalyst.

[0035]

[0035] After the hydroprocessing of the heavy oil, the upgraded heavy oil can be separated into one or more lower boiling hydrocarbon fractions and one or more liquid hydrocarbon fractions. For example, the upgraded heavy oil can be separated using one or more high temperature separation units, an interstage separator that induces a pressure drop, an atmospheric distillation column, or a vacuum distillation column.

[0036]

[0036] These and other advantages and features of the present invention will become more fully apparent from the following description and the appended claims, or may be learned by the practice of the invention as hereinafter described.

[0037]

[0037] To further clarify the above and other advantages and features of the present invention, a more specific description of the present invention is represented by reference to its specific embodiments shown in the accompanying drawings. It is understood that these drawings merely illustrate typical embodiments of the present invention and should not be regarded as limiting its scope. The present invention is described and explained using the accompanying drawings with additional specificity and detail.

Brief Description of the Drawings

[0038]

Figure 1

[0038] Shows a hypothetical molecular structure of asphaltenes.

Figure 2

[0039] Schematically shows an exemplary ebullated bed hydroprocessing system using a dual catalyst system that can be used to hydroprocess heavy oil.

Figure 3A

[0040] Figure 3A schematically shows an exemplary ebullated bed reactor and a separator unit that separates evaporable materials from non-evaporable materials.

Figure 3B

[0041] Figure 3B schematically shows an exemplary slurry phase reactor and a separator unit that separates evaporable materials from non-evaporable materials.

Figure 3C

[0042] Figure 3C schematically shows an exemplary hydrotreating system including a slurry phase reactor, a separator unit that separates evaporable materials from non-evaporable materials, and a fixed bed reactor that further hydrotreats the non-evaporable materials.

Figure 4A

[0043] Figure 4A schematically shows an exemplary ebullated bed hydrotreating system including a plurality of ebullated bed reactors and other processing devices.

Figure 4B

[0044] Figure 4B, similar to Figure 4A, schematically shows an exemplary ebullated bed hydrotreating system including a plurality of ebullated bed reactors, and an inter-stage separator between two of the reactors.

Figure 5

[0045] Figure 5 schematically shows an exemplary mixing system for blending a catalyst precursor into a heavy oil feedstock using a high-boiling hydrocarbon diluent.

Figure 6

[0046] Figure 6 is a flowchart schematically showing an exemplary process for preparing a heavy oil feedstock adjusted using a catalyst precursor and a high-boiling hydrocarbon diluent.

Figure 7A

[0047] Figures 7A - 7B schematically show an exemplary system for preparing a heavy oil feedstock adjusted using a catalyst precursor and a high-boiling hydrocarbon diluent.

Figure 7B

Figure 8A

[0048] Figures 8A - 8B schematically show another exemplary mixing system having parallel mixing lines and bypass lines for preparing a heavy oil feedstock adjusted using a catalyst precursor and a high-boiling hydrocarbon diluent.

Figure 8B

DETAILED DESCRIPTION OF THE INVENTION

[0039] I. Introduction

[0049] A method and system are disclosed herein that are particularly configured to form a conditioned feedstock as a preparation for hydrotreating heavy oil using one or more hydrotreating reactors by mixing a catalyst precursor with a high-boiling hydrocarbon diluent to form a catalyst precursor mixture and then mixing the catalyst precursor mixture with a heavy oil feedstock. The methods and systems of the present disclosure provide for the effective use of dispersed catalysts in ebullated bed, fixed bed, or slurry hydroconversion systems when mid-boiling materials are unavailable or disadvantageous as diluents for the preparation of the diluted precursor mixture.

[0040]

[0050] The high-boiling hydrocarbon diluent can include one or more high-boiling hydrocarbons such as vacuum residue, vacuum tower bottoms, other heavy oil feedstocks, deasphalted heavy oil, and / or a sidestream of a conditioned heavy oil feedstock formed using the methods and systems of the present disclosure. Typically, the high-boiling hydrocarbon has a nominal boiling point above 524 °C. The high-boiling hydrocarbon diluent can optionally contain or be mixed with mid-boiling hydrocarbons such as startup diesel, vacuum gas oil, atmospheric gas, decanted oil, cycle oil, or other hydrocarbons having a nominal boiling point in the range of about 200 °C to 524 °C.

[0041]

[0051] Preferred catalyst precursors are oil-soluble and have a decomposition temperature above which they decompose. Unfortunately, high-boiling hydrocarbons are maintained at temperatures above the decomposition temperature of the preferred catalyst, typically to reduce their viscosity so that they can be easily pumped and processed.

[0042]

[0052] The methods and systems of the present disclosure utilize a cooler to control the temperature of the high-boiling hydrocarbon diluent to prevent significant decomposition of the catalyst precursor when forming the catalyst precursor mixture. In some embodiments, the high-boiling hydrocarbon diluent is cooled to a temperature in the range of about 75 °C to about 150 °C, or about 75 °C to about 125 °C, or about 75 °C to about 95 °C.

[0043]

[0053] In some embodiments, cooling of the high-boiling hydrocarbon diluent is accomplished solely by one or more coolers, such as one or more heat exchangers. In other embodiments, cooling of the high-boiling hydrocarbon diluent includes adding a middle-boiling hydrocarbon that already has a temperature lower than the decomposition temperature of the catalyst precursor.

[0044]

[0054] In some embodiments, a portion of the heavy oil feedstock can be used as a diluent to form a diluent precursor mixture. In other embodiments, a portion of the conditioned feedstock can be used as a diluent to form a diluent precursor mixture. In still other embodiments, the vacuum tower bottom product can be used as a diluent to form a diluent precursor mixture. In yet other embodiments, deasphalted heavy oil can be used as a diluent to form a diluent precursor mixture. When used as a diluent, such materials advantageously have their temperatures reduced before passing through a heat exchanger and being mixed with the catalyst precursor.

[0045] II. Definitions

[0055] The terms "asphaltene" and "asphaltenes" refer to substances in a heavy oil feedstock that are insoluble in paraffinic solvents such as propane, butane, pentane, hexane, and heptane. Asphaltenes can include sheets of condensed ring compounds held together by heteroatoms such as sulfur, nitrogen, oxygen, and metals. Broadly, asphaltenes include a wide range of complex compounds having from 80 to 1200 carbon atoms and, when determined by solution techniques, having molecular weights solely in the range of 1200 to 16,900. Approximately 80 - 90% of the metals in crude oil, which together with a high concentration of non-metallic heteroatoms make the asphaltene molecules in heavy oil resid more hydrophilic and less hydrophobic than other hydrocarbons, are contained in the asphaltene fraction.

[0046]

[0056] Figure 1 shows a hypothetical asphaltene molecular structure developed by A.G. Bridge and collaborators at Chevron. Asphaltenes are typically defined based on the results of insolubility analysis, and two or more of the definitions of asphaltenes may be used. Specifically, the commonly used definition of asphaltenes is the subtraction of toluene-insoluble matter from heptane-insoluble matter (i.e., asphaltenes are soluble in toluene, and precipitates and residues that are insoluble in toluene are not counted as asphaltenes). Asphaltenes defined in this manner may be referred to as "C 7 asphaltenes". Another definition is measured as the subtraction of toluene-insoluble matter from pentane-insoluble matter and is commonly referred to as "C 5 asphaltenes". In the examples of the present invention, the C 7 asphaltene definition is used, but it can be easily replaced with the C 5 asphaltene definition.

[0047]

[0057] "Fouling" refers to the formation of an undesirable phase (fouling substance) that interferes with the process. Fouling substances are typically carbonaceous materials or solids (e.g., precipitates) that accumulate and deposit within the processing apparatus. Fouling of the apparatus can result in shutdown of the apparatus, production losses due to reduced apparatus performance, increased energy consumption due to the insulating effect of fouling substance deposition in heat exchangers or heaters, increased maintenance costs for apparatus cleaning, reduced fractionation efficiency, and reduced reactivity of heterogeneous catalysts. Hydroprocessing apparatuses, such as mixing lines, require periodic maintenance to remove precipitates and other fouling substances.

[0048]

[0058] The "fouling rate of the device" of the hydrocracking reactor can be measured by at least one of (i) the frequency of heat exchanger cleaning required, (ii) the frequency of switching to the preheat exchanger, (iii) the frequency of filter replacement, (iv) the frequency of strainer cleaning or replacement, (v) the rate of decrease in the surface temperature of the device, including inside the device selected from a heat exchanger, a separator, or a distillation column, (vi) the rate of increase in the metal temperature of the furnace tubes, (vii) the rate of increase in the calculated fouling resistance factor of the heat exchanger and the furnace, (viii) the rate of increase in the differential pressure of the heat exchanger, (ix) the cleaning frequency of the atmospheric distillation column and / or the vacuum distillation column, or (x) the frequency of regular maintenance.

[0049]

[0059] "Heavy oil" and "heavy oil feedstock" refer to residual oils remaining from refinery processes such as heavy crude oil, oil sand bitumen, barrel bottoms, and visbreaker bottoms, and any other lower-quality materials that contain a significant amount of high-boiling hydrocarbon fractions, and / or contain a significant amount of asphaltenes that can deactivate heterogeneous catalysts, and / or cause or result in the formation of coke precursors and precipitates. Examples of heavy oil include, but are not limited to, Lloydminster heavy oil, Cold Lake bitumen, Athabasca bitumen, atmospheric tower bottoms, vacuum tower bottoms, residual oil (or "residuum"), residuum pitch, vacuum residues (e.g., Urals VR, Arab Medium VR, Athabasca VR, Cold Lake VR, Maya VR, and Chichimene VR), deasphalted liquids obtained by asphaltenes by solvent deasphalting, asphaltene liquids obtained as by-products of deasphalting, and non-volatile liquid fractions remaining after distillation, thermal separation, solvent extraction, etc. of crude oil, bitumen from tar sands, liquefied coal, oil shale, or coal tar feedstock. As a further example, atmospheric tower bottoms (ATB) can have a nominal boiling point of at least 343 °C, but the cut point can vary between refineries and is understood to be as high as 380 °C. Vacuum tower bottoms can have a nominal boiling point of at least 524 °C, but the cut point can vary between refineries and is understood to be as high as 538 °C or even 565 °C.

[0050]

[0060] "High-boiling hydrocarbon material" and "high-boiling hydrocarbon" refer to hydrocarbons in a processing facility having a nominal boiling point of at least about 524 °C. Examples include, but are not limited to, vacuum residues (produced from crude oil after a series of separation processes including vacuum distillation), vacuum tower bottoms (produced downstream of one or more hydrotreating reactors after a series of separation processes including vacuum distillation), other heavy oil feedstocks, deasphalted heavy oil, and / or conditioned heavy oil feedstocks containing catalyst precursors and / or dispersed catalysts.

[0051]

[0061] "Middle-boiling hydrocarbon materials" and "middle-boiling hydrocarbons" refer to hydrocarbons in a processing facility having a nominal boiling point in the range of about 200°C to about 524°C. Examples include, but are not limited to, vacuum gas oil (typically having a boiling point range of 360°C to 524°C), atmospheric gas oil (typically having a boiling point range of 200°C to 360°C), decant oil or cycle oil (typically having a boiling point range of 360°C to 550°C), or other hydrocarbons having a nominal boiling point in the range of about 200°C to 524°C.

[0052]

[0062] "High-boiling hydrocarbon diluent" refers to one or more high-boiling hydrocarbons that are used as a diluent and mixed with a catalyst precursor to form a pre-dilution precursor mixture. The high-boiling hydrocarbon diluent may optionally contain one or more middle-boiling hydrocarbons in addition to one or more high-boiling hydrocarbons.

[0053]

[0063] "Catalyst precursor" refers to a compound such as an oil-soluble compound containing or preparing one or more catalyst metals such as molybdenum. Examples of catalyst precursors include organometallic complexes or compounds, more specifically, oil-soluble compounds or complexes of transition metals and organic acids having a decomposition temperature or range high enough to avoid substantial decomposition when mixed with a heavy oil feedstock under suitable mixing conditions.

[0054]

[0064] "Pre-dilution precursor mixture" refers to a mixture of a hydrocarbon diluent and a catalyst precursor that is used to disperse the catalyst precursor into a heavy oil feedstock.

[0065] "Hydrocracking" and "hydroconversion" refer to processes whose main purpose is to reduce the boiling point range of heavy oil, and a significant portion of the heavy oil is converted into a product having a boiling point range lower than that of the original feed. Hydrocracking or hydroconversion generally involves the fragmentation of larger hydrocarbon molecules into smaller molecular fragments having a smaller number of carbon atoms and a higher hydrogen-to-carbon ratio. The mechanism by which hydrocracking occurs typically involves the formation of hydrocarbon free radicals during thermal fragmentation, followed by capping the free radicals with hydrogen. The hydrogen atoms or radicals that react with the hydrocarbon free radicals during hydrocracking can be generated at or by the active catalyst sites.

[0055]

[0066] The term "hydrotreating" refers to a process whose main purpose is to remove impurities such as sulfur, nitrogen, oxygen, halides, and trace metals from the feedstock, and to saturate olefins and / or stabilize hydrocarbon free radicals by reacting them with hydrogen rather than reacting them with themselves. The main purpose is not to change the boiling point range of the feedstock. Hydrotreating is most often carried out using a fixed bed reactor, but other hydrotreating reactors can be used, examples of which are fluid bed hydrotreating reactors and slurry phase hydrotreating reactors.

[0056]

[0067] "Hydrocracking" and "hydroconversion" may also involve the removal of sulfur and nitrogen from the feedstock, as well as olefin saturation and other reactions typically associated with "hydrotreating". The terms "hydrotreating" and "hydroconversion" are intended to broadly refer to both the "hydrocracking" and "hydrotreating" processes that define both ends of the spectrum and all points in between along the spectrum.

[0057]

[0068] "Hydrocracking reactor" refers to any vessel in which the hydrocracking of a feedstock (i.e., reduction of the boiling range) in the presence of hydrogen and a hydrocracking catalyst is the main objective. A hydrocracking reactor is characterized by having one or more inlet ports into which heavy oil and hydrogen are introduced, an outlet port from which the upgraded feedstock or material is withdrawn, and sufficient thermal energy to promote the fragmentation of larger hydrocarbon molecules into smaller molecules and cause the formation of hydrocarbon free radicals. Examples of hydrocracking reactors include, but are not limited to, slurry-phase reactors (i.e., two-phase, gas-liquid systems), fluidized-bed reactors (i.e., three-phase, gas-liquid-solid systems), and fixed-bed reactors (i.e., three-phase systems containing a liquid feed that flows downward or upward (typically with hydrogen in co-current flow but in some cases in counter-current flow) through a fixed bed of solid heterogeneous catalyst).

[0058]

[0069] "Hydrocracking temperature" refers to the minimum temperature required to cause significant hydrocracking of the heavy oil feedstock. Generally, the hydrocracking temperature preferably falls within the range of about 399 °C (750 °F) to about 460 °C (860 °F), more preferably within the range of about 418 °C (785 °F) to about 443 °C (830 °F), and most preferably within the range of about 421 °C (790 °F) to about 440 °C (825 °F).

[0059]

[0070] "Gas-liquid slurry-phase hydrocracking reactor" refers to a hydrotreating reactor containing a continuous liquid phase and a gas dispersion phase that forms a "slurry" with gas bubbles in the liquid phase. The liquid phase typically contains a hydrocarbon feedstock that may contain low-concentration dispersed metal sulfide catalyst particles and can behave colloidal or as a pseudo-solute, and the gas phase typically contains hydrogen gas, hydrogen sulfide, and vaporized low-boiling hydrocarbon products. The liquid phase can optionally contain a hydrogen-donating solvent.

[0060]

[0071] When a solid catalyst is used with liquids and gases, the term "gas-liquid-solid, three-phase slurry hydrocracking reactor" is used. The gas may contain hydrogen, hydrogen sulfide, and vaporized low-boiling hydrocarbon products. The term "slurry-phase reactor" is intended to broadly refer to both types of reactors (e.g., those containing dispersed metal sulfide catalyst particles, those containing micrometer-sized or larger particulate catalysts, and those containing both).

[0061]

[0072] "Solid heterogeneous catalyst", "heterogeneous catalyst", and "supported catalyst" refer to catalysts typically used in fluidized bed and fixed bed hydrotreating systems, including catalysts designed primarily for hydrocracking, hydroconversion, hydrodemetallization, and / or hydrotreating. A heterogeneous catalyst typically includes a catalyst support structure having a large surface area and interconnected channels or pores, and fine active catalyst particles such as sulfides of cobalt, nickel, tungsten, and / or molybdenum dispersed within the channels or pores. The pores of the support are typically of a limited size that maintains the mechanical integrity of the heterogeneous catalyst and prevents the destruction and formation of excessive particulates within the reactor. Heterogeneous catalysts can be manufactured as cylindrical pellets, cylindrical extrudates, other shapes such as trilobal, ring-shaped, saddle-shaped, or as spherical solids.

[0062]

[0073] "Dispersed metal sulfide catalyst particles" and "dispersed catalyst" refer to catalyst particles having a particle size of less than 1 μm (submicron, or submicrometer), preferably less than about 500 nm, or less than about 250 nm, or less than about 100 nm, or less than about 50 nm, or less than about 25 nm, or less than about 10 nm, or less than about 5 nm. The term "dispersed metal sulfide catalyst particles" can include molecularly dispersed catalyst compounds or intramolecularly dispersed catalyst compounds. "Dispersed metal sulfide catalyst particles" typically exclude metal sulfide particles and aggregates of metal sulfide particles larger than 1 μm.

[0063]

[0074] "Intramolecularly dispersed catalyst" refers to a catalyst that is essentially "dissolved" in a hydrocarbon feedstock or a suitable diluent, or a catalyst compound that is dissociated from other catalyst compounds or molecules in a hydrocarbon feedstock or a suitable diluent. Very small catalyst particles containing several catalyst molecules (e.g., 15 molecules or less) bound together can be cited.

[0064]

[0075] "Residual dispersed catalyst particles" and "residual dispersed metal sulfide catalyst particles" refer to catalyst particles that remain with hydrocarbon products when transferred from one vessel to another (e.g., from a hydrotreating reactor to a separator and / or another hydrotreating reactor). Residual dispersed metal sulfide catalyst particles can also remain in the liquid residue fraction or pitch after separating hydrocarbon products into distillate and residue or pitch by flash separation, thermal separation, atmospheric distillation, vacuum distillation, or vacuum stripping.

[0065]

[0076] "Adjusted feedstock" refers to a hydrocarbon feedstock that contains dispersed metal sulfide catalyst particles formed in situ within the feedstock during the decomposition of the catalyst precursor and the formation of the active catalyst as a result of the sufficient combination and mixing of the catalyst precursor. The adjusted feedstock includes adjusted heavy oil.

[0066]

[0077] "Upgrading", "upgrade", and "upgraded", when used to describe a hydrogenated or processed feedstock, or a resulting material or product, refer to one or more of the reduction of the molecular weight of the feedstock, the reduction of the boiling point range of the feedstock, the reduction of the asphaltene concentration, the reduction of the hydrocarbon free radical concentration, and / or the reduction of the amount of impurities such as sulfur, nitrogen, oxygen, halides, and metals.

[0067]

[0078] "Severity" refers to the amount of energy introduced into the heavy oil during the hydrogenation process and is related to the operating temperature of the hydrogenation reactor in combination with the duration or residence time (i.e., at the same or similar throughput, a higher temperature is related to a higher severity and a lower temperature is related to a lower severity). An increase in severity generally increases the amount of conversion products produced by the hydrogenation reactor, including both desirable and undesirable products. Conversion and throughput also affect severity. For example, when the temperature rises and the throughput is kept constant, the conversion typically increases for a given feedstock. To maintain the temperature while increasing the throughput that shortens the residence time of the heavy oil in the reactor (i.e., increasing the liquid hourly space velocity), more thermal energy must be added to the system to offset the cooling effect of passing a larger amount of initially lower temperature heavy oil through the reactor per unit time.

[0068]

[0079] Desirable conversion products include hydrocarbons with reduced molecular weight, boiling point, and specific gravity, and these can include end products such as naphtha, diesel, jet fuel, kerosene, wax, fuel oil, etc. Other desirable conversion products include higher boiling hydrocarbons that can be further processed using conventional purification and / or distillation processes. Bottom products of sufficient quality to be useful as fuel oil are another example of desirable conversion products.

[0069]

[0080] Undesirable conversion products include coke, sediment, metals, and other solid substances, which can accumulate in the hydrogenation unit and cause fouling of internal components such as reactors, separators, filters, pipes, towers, heat exchangers, and heterogeneous catalysts. Low-quality conversion products specifically refer to unconverted residual oils that remain after distillation, such as atmospheric tower bottoms ("ATB") or vacuum tower bottoms ("VTB"), which are of too low quality to be useful for fuel oil or other desired uses. By minimizing undesirable conversion products, fouling of the unit and shutdowns required for cleaning the unit are reduced.

[0070]

[0081] In addition to temperature, "severity" may be related to one or both of "conversion rate" and "throughput". Whether an increase in severity is accompanied by an increase in conversion rate and / or an increase or decrease in throughput may depend on the quality of the heavy oil feedstock and / or the material balance of the overall hydrotreating system. For example, if it is desired to convert a larger amount of feedstock and / or provide a larger amount of material to downstream equipment, an increase in severity may, in some cases, be accompanied by an increase in throughput that does not necessarily result in an increase in the fraction conversion rate. This can be exemplified by the case where the residue fraction (ATB and / or VTB) is sold as fuel oil and the amount of this product is reduced by increasing the conversion rate without increasing the throughput. If it is desired to increase the ratio of upgraded material to the residue fraction, in some cases, an increase in conversion rate that does not necessarily result in an increase in throughput may be desired. When the quality of the heavy oil introduced into the hydrotreating reactor varies, it may be desirable to selectively increase or decrease one or both of the conversion rate and throughput to maintain the desired ratio of upgraded material to residue fraction and / or the desired absolute amount of the final product(s) produced.

[0071]

[0082] "Conversion rate" and "fraction conversion" often refer to the percentage expressed as the percentage of heavy oil converted to low-boiling substances and / or substances of lower molecular weight. The conversion rate is expressed as the percentage of the initial residue oil content (i.e., the components having a boiling point exceeding the defined residue cut point) converted to products having a boiling point below the defined cut point. The definition of the residue cut point can vary and can include nominal 524 °C (975 °F), 538 °C (1000 °F), 565 °C (1050 °F), etc. This can be measured by distillation analysis of the feed stream and product stream that determines the concentration of components having a boiling point exceeding the defined cut point. The fraction conversion rate is expressed as (F - P) / F, where F is the amount of residue oil in the combined feed stream and P is the amount of residue oil in the combined product stream, and the residue oil content of both the feed and product is based on the same cut point definition. The amount of residue oil is often defined based on the mass of components having a boiling point exceeding the defined cut point, but volume or molar definitions can also be used.

[0072]

[0083] The conversion rate of asphaltenes can be different from the overall conversion rate of heavy oil. For the purposes of this disclosure, a useful definition of the asphaltene conversion rate can be defined as follows, which results in a decimal fraction between 0 and 1 that can be converted to a percentage by multiplying by 100, based on the relative amounts of asphaltenes in the unused feedstock and the upgraded product. Conv = [Asph(unused feed) - Asph(product)] / Asph(unused feed) The asphaltene content of the recycle stream is internal to the process. If the conversion rate of asphaltenes is too low compared to the conversion rate of heavy oil as a whole, asphaltene recycle accumulation can occur.

[0073]

[0084] "Throughput" refers to the amount (mass or volume) of feedstock introduced into a hydrotreating reactor per unit time. Throughput can be expressed in volumetric terms such as barrels per hour or per day, or in mass terms such as metric tons per hour or per day. In normal usage, throughput is defined as the mass or volumetric feed rate of the heavy oil feedstock itself (e.g., vacuum tower bottoms, etc.). This definition usually excludes diluents or other components whose amounts may be added to or included in the overall feed to the hydroconversion unit, although a definition including those other components may also be used.

[0074]

[0085] "Space velocity" and "liquid space velocity" are related to the throughput of a particular reactor or reactor size and are normalized to remove the reactor size (volume). Thus, a larger reactor can have twice the throughput, but can have the same space velocity as a reactor with half the volume size. Thus, an increase in space velocity typically scales with an increase in throughput for a given reactor size. Space velocity is inversely proportional to the residence time of the heavy oil in the reactor of a given reactor size.

[0075]

[0086] "Rate of production of the converted product" is an absolute rate that can be expressed in volumetric terms such as barrels per hour or per day, or in mass terms such as metric tons per hour or per day. The "rate of production of the converted product" should not be confused with yield or efficiency, which are sometimes incorrectly called "rates" (e.g., rate of production per unit feed rate, or rate of production per unit of converted feed). It is understood that the actual numerical values of both the initial rate of production of the converted product and the increase in the rate of production of the converted product are specific to an individual production facility and depend on the capabilities of that facility. Thus, it is useful to compare the production rates of the unit or facility in question before and after reforming, rather than for different units or facilities built with different capabilities.

[0076] III. Exemplary Hydrotreating System

[0087] Figures 2 - 4B illustrate exemplary hydrotreating reactors and systems that can be used with or benefit from the disclosed methods and systems for mixing a catalyst precursor into heavy oil using a high - boiling hydrocarbon diluent to form an adjusted heavy oil feedstock. When the adjusted feedstock is heated, the catalyst precursor decomposes in - situ to form dispersed metal sulfide catalyst particles within the heavy oil feedstock. The heating can be accomplished upstream and / or within the hydrotreating reactor.

[0077]

[0088] The disclosed methods and systems can be used or located at any location within the illustrated hydrotreating system. Generally, the methods and systems are utilized or located upstream of a hydrotreating reactor configured to operate using an in - situ generated dispersed metal sulfide catalyst in heavy oil. The disclosed methods and systems provide for the continuous introduction of the catalyst precursor into the heavy oil and the in - situ formation of dispersed metal sulfide catalyst particles within the heavy oil, while being able to utilize a high - boiling hydrocarbon material as a diluent without prematurely decomposing the catalyst precursor.

[0078]

[0089] In the blending methods and systems of the present disclosure, feedstocks that can be hydrotreated using one or more hydrotreating reactors include, but are not limited to, one or more heavy crudes, oil sand bitumens, bottoms of barrel fractions from crude oil, atmospheric column bottoms, vacuum column bottoms, coal tar, liquefied coal, other residual oil fractions, pyrolysis oils, and deasphalted oils, and may include any desired fossil fuel feedstock and / or fractions thereof. Heavy oils and residual oils can include significant fractions of high-boiling hydrocarbons (i.e., nominally 343 °C (650 °F) or higher, more specifically nominally 524 °C (975 °F) or higher) and / or asphaltenes. As mentioned above and illustrated in FIG. 1, asphaltenes are complex hydrocarbon molecules with a relatively low hydrogen-to-carbon ratio that results from a significant number of condensed aromatic and naphthene rings with paraffin side chains. Thin films consisting of condensed aromatic and naphthene rings are held together by heteroatoms such as sulfur or nitrogen, polymethylene cross-links, thioether bonds, and / or vanadium and nickel complexes. Also, the asphaltene fraction contains compounds in which asphaltenes also have more sulfur and nitrogen than the remainder of the crude oil or vacuum residue, and are also formed with a higher concentration of carbon (i.e., those that form coke precursors and precipitates).

[0079]

[0090] FIG. 2 schematically shows an exemplary fluidized bed hydrotreating system 200 that utilizes a dual catalyst system of dispersed metal sulfide catalyst particles and a heterogeneous fluidized bed catalyst. The fluidized bed hydrotreating system 200 includes a fluidized bed reactor 230 and a separator 204 (e.g., a high-temperature separator, an inter-stage pressure differential separator, or a distillation column). The fluidized bed reactor 230 is similar to that used in the LC-Fining hydrocracking system developed by C-E Lummus. The catalyst precursor 202 is blended with a hydrocarbon diluent 203 in one or more premixers 206 to form a diluted precursor mixture 209. The diluted precursor mixture 209 is added to the heavy oil feedstock 208 and blended with the feedstock using a mixing system 210 to form a conditioned feedstock 211.

[0080]

[0091] The adjusted feedstock 211 is supplied to a surge tank 212 having a pump-around loop 214 to achieve further mixing and dispersion of the catalyst precursor 202 within the feedstock 208. A bypass line (not shown) returns any heavy oil that bypasses a mixing line (not shown) to a common discharge line (not shown) and / or directly supplies heavy oil to the surge tank 212. The surge tank 212 and the pump-around loop 214 advantageously achieve further mixing of the catalyst precursor into the heavy oil, including the heavy oil from the bypass line. The adjusted feed material from the surge tank 212 is pressurized by one or more pumps 216, passed through a preheater 218, and supplied into a fluidized-bed hydrotreating reactor 230 together with hydrogen gas 220 through one or more inlet ports 236 located at or near the bottom of the fluidized-bed reactor 230.

[0081]

[0092] The fluidized-bed reactor 230 includes a hydrocarbon material 226 and an expanded catalyst zone 242 that includes a heterogeneous catalyst 244 typical of fluidized-bed reactors that is maintained in an expanded or fluidized state against gravity by the upward movement of the liquid hydrocarbon 226 and gas. A lower heterogeneous-catalyst-free zone 248 is located below a distributor grid plate that defines the bottom of the expanded catalyst zone 242, and an upper heterogeneous-catalyst-free zone 250 is located above the expanded catalyst zone 242. The dispersed metal sulfide catalyst particles 224 are dispersed throughout the hydrocarbon material 226 within the fluidized-bed reactor 230 included in the expanded catalyst zone 242 and the heterogeneous-catalyst-free zones 248, 250, thereby promoting beneficial upgrade reactions in the absence of the heterogeneous catalyst 244.

[0082]

[0093] The funnel-shaped recycle cup 256 that supplies the recycle channel 252 connected to the boiling pump 254 continuously recycles the hydrocarbon material 226 from the upper heterogeneous catalyst-free zone 250 to the lower heterogeneous catalyst-free zone 248. The downward suction by the recycle cup 256 at the upper part of the recycle channel 252 causes the hydrocarbon material 226 containing the dispersed catalyst particles 224 to pass downward from the upper heterogeneous catalyst-free zone 250 through the recycle channel 252 and be drawn out to the bottom of the fluidized bed reactor 230 by the boiling pump 254. The recycled hydrocarbon material 226 is blended with a fresh feedstock containing dispersed metal sulfide catalyst particles (and / or catalyst precursors) and hydrogen gas 220.

[0083]

[0094] The unused heterogeneous catalyst 244 can be periodically introduced into the fluidized bed reactor 230 through the catalyst inlet pipe 258, and the spent heterogeneous catalyst 244 can be periodically withdrawn through the catalyst withdrawal pipe 260. The dispersed metal sulfide catalyst particles 224 provide additional catalytic activity within the expanded catalyst zone 242, the recycle channel 252, and the lower and upper heterogeneous catalyst-free zones 248, 250. The catalytic addition of hydrogen to the hydrocarbon outside the heterogeneous catalyst 244 often reduces or minimizes the formation of deposits and coke precursors that contribute to the inactivation of the heterogeneous catalyst and system fouling.

[0084]

[0095] The fluidized bed reactor 230 further includes an outlet port 238 from which the converted material 240 is withdrawn, located at or near the upper part thereof. The converted material 240 is introduced into a separator 204 that separates the volatile fraction 205 from the residue oil fraction 207. The volatile fraction 205 is withdrawn from the upper part of the high-temperature separator 204, and the residue oil fraction 207 is withdrawn from the bottom of the high-temperature separator 204. The residue oil fraction 207 contains residual metal sulfide catalyst particles schematically shown as catalyst particles 224. Optionally, at least a part of the residue oil fraction 207 can be returned to the fluidized bed reactor 230 for reuse to form a part of the feedstock and supply additional dispersed metal sulfide catalyst particles. Alternatively, the residue oil fraction 207 may be further processed using downstream processing devices such as another fluidized bed reactor, a distillation column, a deasphalting unit, etc. In that case, the separator 404 may be a stage separator. A part of the residue oil fraction 207 can be used as part or all of the hydrocarbon oil diluent 203 added to the premixer 206 to form the diluted catalyst precursor 209.

[0085]

[0096] Figure 3A schematically shows another type of fluidized bed hydrotreating reactor 310 having a different recycle system typical of the H-Oil hydrocracking system developed by Hydrocarbon Research, Inc. and currently licensed by Axens. The fluidized bed reactor 310 includes an inlet port 312 into which a heavy oil feedstock 314 and pressurized hydrogen gas 316 are introduced, and an outlet port 318 from which the upgraded hydrocarbon material 320 is withdrawn.

[0086]

[0097] The expanded catalyst zone 322 containing the heterogeneous catalyst 324 is defined by a distributor grid plate 326 that separates the expanded catalyst zone 322 from the lower catalyst-free zone 328 below the distributor grid plate 326, and an upper end 329 that defines an approximate boundary between the expanded catalyst zone 322 and the upper catalyst-free zone 330. The dotted boundary line 331 schematically indicates the approximate level of the heterogeneous catalyst 324 when not in an expanded or fluidized state. The dispersed metal sulfide catalyst particles 325 are dispersed throughout the hydrocarbon materials in both the fluidized bed reactor 310, the expanded catalyst zone 322, and the lower and upper heterogeneous catalyst-free zones 228, 230.

[0087]

[0098] The hydrocarbons and other materials in the fluidized bed reactor 310 are continuously recycled by a recycle channel 332 connected to a fluidizing pump 334 located outside the reactor 310. The materials are drawn from the upper heterogeneous catalyst-free zone 330 through a funnel-shaped recycle cup 336. The recycle cup 336 serves to separate hydrogen bubbles from the recycled materials passing through the recycle channel 332 and prevent cavitation of the fluidizing pump 334. The recycled materials enter the lower heterogeneous catalyst-free zone 328 through a discharge bell cap 343 where it is blended with the unused heavy oil feedstock 314 and hydrogen gas 316. This mixture passes upward through the distributor grid plate 326 and into the expanded catalyst zone 322. Unused heterogeneous catalyst can be periodically introduced into the expanded catalyst zone 322 through a catalyst inlet tube 336 and spent heterogeneous catalyst can be periodically withdrawn through a catalyst discharge tube 340.

[0088]

[0099] The main difference between the H-Oil fluidized bed reactor 310 illustrated in FIG. 3A and the LC-Fining fluidized bed reactor 200 illustrated in FIG. 2 is the location of the fluidizing pump. The fluidizing pump 334 within the H-Oil reactor 310 is located outside the reactor chamber. The recycled materials are introduced through a recycle port equipped with a distributor cap 343 at the bottom of the fluidized bed reactor 310. The distributor cap 343 assists in evenly distributing the materials passing through the lower catalyst-free zone 328.

[0089]

[0100] The upgraded material 320 is withdrawn from the outlet port 318 of the fluidized bed reactor 310 and introduced into a separator 342 (e.g., a high-temperature separator, an inter-stage pressure differential separator, an atmospheric distillation column, or a vacuum distillation column). The separator 342 is configured to separate the volatile fraction (gas and distillate) 346 from the non-volatile fraction (or liquid) 348. The distillate and gas 346 are removed at one location (e.g., the top) of the separator 342, and the non-volatile fraction 348 containing liquid hydrocarbons and residual dispersed metal sulfide catalyst particles is removed from another location (e.g., the bottom) of the separator 342.

[0090]

[0101] FIG. 3B schematically depicts a hydrotreating system 300 that includes a slurry-phase reactor 302 and a separator 304 (e.g., a high-temperature separator, an inter-stage pressure differential separator, or a distillation column). A heavy oil feedstock 306 is blended and conditioned with a catalyst precursor mixture 308 using a mixing system 310. The mixing 308 of the dilution precursor includes a catalyst mixed with a diluent formed in a premixer (not shown). The conditioned feedstock from the mixing system 310 is pressurized by a pump 312, which can also serve as a multi-stage mixing device to further disperse the catalyst precursor throughout the entirety of the heavy feedstock 306, passes through a preheater 314, and is supplied to the slurry-phase reactor 302 together with hydrogen gas 316 through one or more input ports 318 located at or near the bottom of the slurry-phase reactor 302.

[0091]

[0102] The agitator 320 at the bottom of the slurry reactor 302 induces mixing within the liquid phase, thereby helping to evenly disperse the heat generated by the hydrocracking reaction. Alternatively, or in addition to the agitator 320, the slurry reactor 302 may include recycle channels, recycle pumps, and a distributor grid plate (not shown) to promote a more uniform dispersion of reactants, catalyst, and heat, as in a conventional fluidized bed reactor (see FIGS. 2 and 3A). Hydrogen is schematically represented as gas bubbles 322, and the dispersed metal sulfide catalyst particles are schematically represented as catalyst particles 324 within the reactor 302. It is understood that the gas bubbles 322 and catalyst particles 324 are shown oversized for viewing in the drawing. In reality, they cannot be seen with the naked eye.

[0092]

[0103] The heavy oil feedstock 306 is catalytically upgraded in the slurry reactor 302 in the presence of hydrogen 316 and the dispersed metal sulfide catalyst 324 to form an upgraded hydrocarbon product 326. The upgraded product 326 is continuously withdrawn from the slurry reactor 302 through an output port 328 located at or near the top of the reactor 302 and then, optionally, after passing through optional hydrotreating equipment 330, is fed to a separator 304 (e.g., a high-temperature separator and / or a distillation column). The upgraded product 326 fed to the separator 304 contains residual catalyst particles schematically represented as particles 324' and residual hydrogen schematically represented as bubbles 322', which can continue to promote the beneficial upgrading reaction and reduce fouling of the apparatus. The separator 304 separates the volatile fraction 305 from the non-volatile fraction 307. The volatile fraction 305 is withdrawn from the top of the high-temperature separator 304, and the non-volatile fraction 307 is withdrawn from the bottom of the high-temperature separator 304.

[0093]

[0104] Figure 3C schematically represents a hydrotreating system 300 including a slurry-phase reactor 302, a high-temperature separator 304, and a fixed-bed reactor 360. The upgraded hydrocarbon material 326 contains residual dispersed metal sulfide catalyst particles schematically represented as particles 324' within the high-temperature separator 304. The liquid fraction 307 and the residual dispersed metal sulfide catalyst particles 324' from the high-temperature separator 304 are introduced into the fixed-bed reactor 360 for further hydrotreating. The fixed-bed reactor 360 may be designed to perform hydrocracking and / or hydrotreating reactions depending on the operating temperature and / or the type of solid-supported catalyst used within the fixed-bed reactor 360.

[0094]

[0105] More specifically, the fixed-bed reactor 360 includes an input port 362 into which the liquid fraction 307 and make-up hydrogen gas 364 are introduced at the top, and an output port 366 from which the further hydrotreated material 388 is withdrawn at the bottom. The fixed-bed reactor 360 further includes a plurality of vertically stacked and spaced catalyst beds 370 containing a packed porous supported catalyst. Above each catalyst bed 370 is a distributor grid 372 that helps to more uniformly distribute the flow of feedstock passing downward through the catalyst bed 370. Catalyst-free zones 374 exist above and below each catalyst bed 370. The residual catalyst particles 324' continue to be dispersed throughout the feedstock within the fixed-bed reactor 360 in both the catalyst beds 370 and the catalyst-free zones 374, further promoting beneficial upgrading reactions. Auxiliary ports 376 may be provided in the center and / or bottom of the fixed-bed reactor 360 into which cooling oil and / or hydrogen quench can be introduced to cool the heat generated by the hydrotreating reaction and control the reaction rate, thereby helping to prevent the formation of coke precursors and deposits and / or excess gas within the fixed-bed reactor 360.

[0095]

[0106] Figure 4A schematically shows a fluidized bed hydrotreating system 400 comprising a plurality of fluidized bed reactors 410. An example of the hydrotreating system 400 is an LC-Fining or H-Oil hydrotreating unit and may include three fluidized bed reactors 410a, 410b, 410c in series to upgrade a feedstock 412. The feedstock 412 from the surge tank 414 is pressurized, preheated, and introduced into the first fluidized bed reactor 410a together with hydrogen gas 416, and both pass through their respective heaters before entering the first reactor 410a. The upgraded hydrocarbon material 420a from the first fluidized bed reactor 410a is introduced into the second fluidized bed reactor 410b together with additional hydrogen gas 416. The upgraded hydrocarbon material 420b from the second fluidized bed reactor 410b is introduced into the third fluidized bed reactor 410c together with additional hydrogen gas 416.

[0096]

[0107] One or more inter-stage separators (not shown) may optionally be interposed between the first and second fluidized bed reactors 410a and 410b and / or between the second and third fluidized bed reactors 410b and 410c to remove lower boiling fractions and gases from the non-volatile fraction containing liquid hydrocarbons and residual dispersed metal sulfide catalyst particles. It should be understood that it may be desirable to remove lower alkanes such as hexane and heptane, which are poor solvents for asphaltenes, although they are beneficial fuel products. Removal of volatile materials between the plurality of reactors improves the production of the upgraded product and increases the solubility of asphaltenes in the liquid hydrocarbon material fed to the downstream reactor(s). Both improve the efficiency of the overall hydrotreating system.

[0097]

[0108] The upgraded hydrocarbon material 420c from the third fluidized bed reactor 410c is sent to a high-temperature separator 442a that separates a volatile fraction and a non-volatile fraction. The volatile fraction 446a passes through a heat exchanger 450 that removes heat that can be used to preheat the hydrogen gas 416 before being supplied to the first fluidized bed reactor 410a. The somewhat cooled volatile fraction 446a is sent to an intermediate-temperature separator 442b where the remaining volatile fraction 446b is separated from a liquid fraction 448b that can result from the cooling by the heat exchanger 450. The remaining volatile fraction 446b is sent to a downstream low-temperature separator 442c for further separation into a gas fraction 452c and a degassed liquid fraction 448c.

[0098]

[0109] The liquid fraction 448a from the high-temperature separator 442a is combined with the liquid fraction 448b resulting from the intermediate-temperature separator 442b, sent to a low-pressure separator 442d where a hydrogen-rich gas 452d is separated from the degassed liquid fraction 448d, and sent to a backend system 460 that includes one or more distillation towers including a vacuum distillation tower together with the degassed liquid fraction 448c from the low-temperature separator 442c, and the material is fractionated into products.

[0099]

[0110] The gas fraction 452c from the low-temperature separator 442c is purified into offgas, purge gas, and hydrogen gas 416. The hydrogen gas 416 is compressed, mixed with makeup hydrogen gas 416a, passed through the heat exchanger 450, and introduced into the first fluidized bed reactor 410a together with the feedstock 412 or directly into the second and third fluidized bed reactors 410b and 410c.

[0100]

[0111] FIG. 4B schematically shows a fluidized bed hydrotreating system 400 with a plurality of fluidized bed reactors, similar to the system shown in FIG. 4A, but shows an inter-stage separator 421 interposed between the second and third fluidized reactors 410b and 410c (although the inter-stage separator 421 (or other separator) may be interposed between the first and second fluidized reactors 410a and 410b). As shown, the effluent from the second stage fluidized reactor 410b enters an inter-stage separator 421 which can be a high pressure high temperature separator. The liquid fraction from the separator 421 is combined with a portion of the recycled hydrogen from line 416 and fed to the third stage reactor 410c. The vapor fraction from the inter-stage separator 421 bypasses the third stage reactor 410c, is mixed with the effluent from the third stage reactor 410c, and then enters the high pressure high temperature separator 442a.

[0101]

[0112] Thereby, the lighter, more saturated components formed in the first two reactor stages 410a, 410b can bypass the third stage reactor 410c. This advantage is (1) a reduction in the vapor load on the third stage reactor 410c, which increases the volumetric utilization of the third stage reactor for converting the remaining heavy components, and (2) a reduction in the concentration of the "inverse solvent" components (saturates), which can destabilize (e.g., precipitate) the asphaltenes in the third stage reactor 410c.

[0102]

[0113] The hydrotreating system is typically configured and operated to promote more severe hydrocracking reactions than less severe hydrotreating reactions such as hydrotreating. Hydrocracking involves the reduction of the molecular weight of larger hydrocarbon molecules and / or the breaking of carbon-carbon molecular bonds such as the ring opening of aromatic compounds. On the other hand, hydrotreating mainly involves the hydrogenation of unsaturated hydrocarbons where the breaking of carbon-carbon molecular bonds is minimal or not at all.

[0103]

[0114] To promote more severe hydrocracking over less severe hydrotreating reactions, the hydrotreating reactor(s) is / are preferably operated at a temperature in the range of about 750°F (399°C) to about 860°F (460°C), more preferably in the range of about 780°F (416°C) to about 830°F (443°C), and preferably at a pressure in the range of about 1000 psig (6.9 MPa) to about 3000 psig (20.7 MPa), more preferably in the range of about 1500 psig (10.3 MPa) to about 2500 psig (17.2 MPa), and preferably for a liquid hourly space velocity in the range of -1 about 0.05 hour -1 to about 0.45 hour, more preferably in the range of about 0.1 hour -1 to about 0.35 hour. -1 The difference between hydrocracking and hydrotreating can also be expressed in terms of the residue conversion rate (hydrocracking results in substantial conversion of higher boiling hydrocarbons to lower boiling hydrocarbons, while hydrotreating does not).

[0104]

[0115] The hydrotreating system disclosed herein can achieve a total residue conversion rate in the range of about 60% to about 95%, preferably in the range of about 75% to about 90%. The preferred conversion rate range typically depends on the type of feedstock, as the processing difficulty varies between different feedstocks.

[0105]

[0116] Operating a fluidized bed reactor using a dual catalyst system can result in the same or reduced fouling of the apparatus compared to operating a fluidized bed reactor using only heterogeneous catalysts. For example, when using a dual catalyst system instead of heterogeneous catalysts alone, the rate of fouling of the apparatus can result in one or more of the following benefits: (i) reduced frequency of heat exchanger shutdown and / or distillation column shutdown for cleaning, (ii) reduced frequency of filter and strainer replacement or cleaning, (iii) reduced frequency of switching to a spare heat exchanger, (iv) reduced rate of decrease in the surface temperature of apparatus such as heat exchangers, separators or distillation columns, (v) reduced rate of increase in the metal temperature of furnace tubes, and (vi) reduced rate of increase in the calculated fouling resistance factor of heat exchangers.

[0106] IV. Method and System for Mixing a Catalyst Precursor into Heavy Oil Using a High-Boiling Hydrocarbon Diluent

[0117] FIG. 5 illustrates an exemplary mixing system and corresponding method for producing a heavy oil feedstock conditioned using one or more high-boiling hydrocarbons as diluents to form a pre-diluted precursor mixture. FIG. 6 illustrates an exemplary method for producing a well-mixed and conditioned heavy oil feedstock using one or more high-boiling hydrocarbons as diluents to form a pre-diluted precursor mixture. FIGS. 7A-8B illustrate exemplary mixing systems for mixing a catalyst precursor into a heavy oil feedstock using a pre-diluted precursor mixture formed from a catalyst precursor and a high-boiling hydrocarbon diluent.

[0107]

[0118] FIG. 5 schematically shows an exemplary mixing system 500 and its implied method for forming a conditioned heavy oil feedstock 514 by mixing a catalyst precursor 504 into a heavy oil feedstock 502 using a high-boiling hydrocarbon diluent 506. The high-boiling hydrocarbon diluent 506 is first mixed with the catalyst precursor 504 to form a pre-diluted precursor mixture 510 using a premixer 508. A mid-boiling hydrocarbon diluent 520 can optionally be added to the premixer 508 and / or the cooler 516 to form a blended high-boiling hydrocarbon diluent and used to produce the pre-diluted precursor mixture 510, which is then mixed with the heavy oil feedstock 502 by a main mixing system 512 to form the conditioned feedstock 514. The main mixing system 512 can include one or more static in-line mixers and / or one or more high-shear mixers.

[0108]

[0119] The high-boiling hydrocarbon diluent 506 includes at least one high-boiling hydrocarbon material having a nominal boiling point of at least 524 °C that is cooled using a cooler 516 before being mixed with the catalyst precursor 504. The cooler may include one or more heat exchangers or other cooling devices known in the art. In some embodiments, the high-boiling hydrocarbon diluent 506 includes a portion of the heavy oil feedstock 502. To achieve this, a line provides a side stream of the heavy oil feedstock 502 to the cooler 516. In other embodiments, the high-boiling hydrocarbon diluent 506 includes a portion of the conditioned heavy oil feedstock 514. To achieve this, a line provides a side stream of the conditioned feedstock 514 to the cooler 516. In still other embodiments, the high-boiling hydrocarbon diluent 506 includes, for example, a vacuum column bottom product 518 from a vacuum distillation column used to separate upgraded products from a hydrotreating system, such as the hydrotreating system illustrated in FIGS. 2-4B. In yet other embodiments, the high-boiling hydrocarbon diluent includes heavy oil from a deasphalted oil (not shown) or other high-boiling hydrocarbon or process (not shown).

[0109]

[0120] The medium-boiling hydrocarbon diluent 520 can optionally be used with and / or form a portion of the high-boiling hydrocarbon diluent 506 and the catalyst precursor 504 to form a dilution precursor mixture 510 and may include one or more medium-boiling hydrocarbons having a nominal boiling point in the range of about 200 °C to about 524 °C. Non-limiting examples include vacuum gas oil, atmospheric gas oil, and cycle oil.

[0110]

[0121] The main mixing system 512 used to mix the diluted precursor mixture 510 with the heavy oil feedstock 502 can include any mixer or combination of mixers capable of blending the diluted precursor mixture 510 into the heavy oil feedstock 502. Examples include the mixing devices illustrated in FIGS. 7A - 8B and are discussed more fully below. Examples of mixers that can be included in the main mixing system 512 include, but are not limited to, one or more static in-line mixers, one or more high-shear mixers, surge tanks, and / or one or more high-pressure pumps used to introduce the feedstock 514 conditioned to a hydrotreating reactor (not shown).

[0111]

[0122] FIG. 6 is a flowchart illustrating an exemplary method for forming a well-mixed and conditioned feedstock that includes a catalyst precursor that is fully mixed and blended, for example, substantially homogeneously with a heavy oil feedstock. When heated, the well-mixed and conditioned feedstock can form dispersed metal sulfide catalyst particles in situ within the heavy oil feedstock.

[0112]

[0123] The first step includes providing a high-boiling hydrocarbon diluent that is mixed with the catalyst precursor to form the diluted precursor mixture. The high-boiling hydrocarbon diluent can include one or more high-boiling hydrocarbon materials, such as a portion of one or more heavy oil feedstocks, a portion of the conditioned feedstock, a vacuum tower bottom product from a crude oil distillation or hydrotreating system, deasphalted oil, or other hydrocarbon materials having a nominal boiling point of at least about 350°C, preferably at least about 400°C, more preferably at least about 450°C, most preferably at least about 500°C, for example, at least about 524°C.

[0113]

[0124] In some embodiments, the high-boiling hydrocarbon diluent is at a temperature that is too high to be mixed with the catalyst precursor because, for example, it causes premature thermal decomposition and aggregation of the precursor before it can be properly mixed with the high-boiling hydrocarbon diluent to form a diluted precursor mixture. For example, the heavy oil feedstock may be maintained at a temperature in the range of about 125°C to about 200°C depending on its viscous properties. The adjusted feedstock (after addition and mixing of the dispersed catalyst) may be at a higher temperature of about 160°C to about 300°C. The vacuum column bottom product of the hydroconversion process or unit may also be at a higher temperature of about 150°C to about 300°C.

[0114]

[0125] In such cases, the method includes the step of cooling the high-boiling hydrocarbon diluent to a temperature below the decomposition temperature of the catalyst precursor. This can be achieved using a cooler known in the art such as one or more heat exchangers. Depending on the high-boiling hydrocarbon diluent(s) being used, care should be taken to sufficiently cool the high-boiling hydrocarbon diluent to prevent significant thermal decomposition of the catalyst precursor when mixing it while ensuring that the high-boiling hydrocarbon diluent is kept at a sufficiently high temperature so that it can flow through the mixing device and conduits. To address this issue, the present invention provides a cooler for controlling the temperature of the high-boiling hydrocarbon diluent. The selection and control of this temperature are important because the high-boiling hydrocarbon material must be at a sufficiently low viscosity to be fluid and mixable, but not so low as to avoid undesirable aggregation of the catalyst precursor. In view of the foregoing, the high-boiling diluent can be cooled to a temperature in the range of about 75°C to about 150°C. Preferably, the temperature can be cooled to a temperature in the range of about 75°C to about 125°C. More preferably, the temperature can be cooled to a temperature in the range of about 75°C to about 95°C.

[0115]

[0126] In some embodiments, optionally, at least a portion of the cooling can be provided by mixing a high-boiling hydrocarbon diluent with a mid-boiling hydrocarbon diluent that is already at a temperature lower than the decomposition temperature of the catalyst precursor. The degree of any such cooling depends on the temperature of the high-boiling hydrocarbon diluent, the temperature of the mid-boiling hydrocarbon diluent, the relative amounts of the high-boiling and mid-boiling hydrocarbon diluents, and the target temperature of the combined diluent.

[0116]

[0127] When the temperature of the high-boiling hydrocarbon diluent is appropriately adjusted to be compatible with the catalyst precursor, the process includes the step of mixing the catalyst precursor with the cooled high-boiling hydrocarbon diluent to form a diluted precursor mixture. This can be carried out using one or more mixers known in the art and / or disclosed herein. The catalyst precursor is preferably mixed with a hydrocarbon diluent at a temperature lower than the temperature at which a significant portion of the catalyst precursor decomposes. The mixing may be carried out at a temperature in the range of about 40°C (104°F) to about 250°C (482°F), in the range of about 60°C (140°F) to about 200°C (392°F), or in the range of about 75°C (167°F) to about 125°C (257°F) to form the diluted precursor mixture. The temperature at which the diluted precursor mixture is formed may depend on the decomposition temperature and / or other characteristics of the catalyst precursor utilized, and / or the characteristics of the hydrocarbon diluent such as viscosity.

[0117]

[0128] The duration of the mixing may be in the range of about 0.1 second to about 5 minutes, in the range of about 0.5 second to about 1 minute, or in the range of about 1 second to about 10 seconds.

[0129] The ratio of the catalyst precursor to the hydrocarbon diluent is on a weight basis, preferably in the range of about 1:1000 to about 1:1, more preferably in the range of about 1:500 to about 1:10, and most preferably in the range of about 1:300 to about 1:50 (e.g., 1:600, 1:400, 1:300, 1:200, 1:100 or 1:60). The amount of the catalyst metal (e.g., molybdenum) in the diluted precursor mixture is preferably in the range of about 100 ppm by weight to about 7000 ppm by weight of the diluted precursor mixture, more preferably in the range of about 300 ppm by weight to about 4000 ppm by weight (e.g., 250 ppm by weight, 500 ppm by weight, 750 ppm by weight, or 2500 ppm by weight).

[0118]

[0130] The diluted precursor mixture is then mixed with the heavy oil feedstock using one or more mixers to form an adjusted heavy oil feedstock. The mixer used in this step can be any mixer or combination of mixers capable of blending the diluted precursor mixture into the heavy oil feedstock, e.g., one or more static in-line mixers, one or more high-shear mixers, surge tanks, and / or one or more high-pressure pumps used to introduce the adjusted feedstock into the hydrotreating reactor.

[0119]

[0131] The step of mixing the diluted precursor mixture with the heavy oil feedstock may be in the range of about 0.1 second to about 5 minutes, in the range of about 0.5 second to about 3 minutes, or in the range of about 1 second to about 1 minute.

[0132] The heavy oil feedstock and the diluted precursor mixture are advantageously mixed at a temperature in the range of about 40°C (104°F) to about 350°C (662°F), or in the range of about 60°C (140°F) to about 300°C (572°F), or in the range of about 75°C (167°F) to about 250°C (482°F) to give an adjusted feedstock.

[0120]

[0133] The catalyst precursor is pre-mixed with a hydrocarbon diluent to form a pre-diluted precursor mixture, which is then mixed with the heavy oil feedstock, so that the feedstock may be at a temperature above the decomposition temperature of the catalyst precursor. In some cases, the hydrocarbon diluent shields individual catalyst precursor molecules during mixing, preventing them from aggregating to form larger particles, thermally insulating the catalyst precursor molecules from the heat from the heavy oil temporarily, and promoting the dispersion of the catalyst precursor molecules throughout the feedstock sufficiently rapidly before they are decomposed to liberate the metal. Additionally, further heating of the feedstock may be required to liberate hydrogen sulfide from sulfur-bearing molecules in the heavy oil to form metal sulfide catalyst particles. In this way, the gradual dilution of the catalyst precursor enables a high level of dispersion within the heavy oil, resulting in the formation of highly dispersed metal sulfide catalyst particles even when the feedstock is at a temperature exceeding the decomposition temperature of the catalyst precursor.

[0121]

[0134] The high-boiling hydrocarbon diluent can be used in an amount in the range of 0.1 volume % to 10 volume %, or about 0.5 volume % to about 5 volume %, of the total feedstock going to the hydrotreating unit. Sources of high-boiling diluents (e.g., heavy oil feedstock, conditioned heavy oil feedstock, vacuum residue, deasphalted heavy oil, and vacuum tower bottoms) can be used individually at 0.1% to 10%, or about 0.5% to about 5%, of the total heavy oil feedstock, or they can be used in any combination that together is 0% to 10% or about 0.5% to about 5% of the total heavy oil feedstock. Such sources of high-boiling hydrocarbon diluents can optionally be combined individually with one or more mid-boiling hydrocarbons, or with any combination of one or more heavy boiling diluent sources that together is 0% to 10% of the total heavy oil feedstock.

[0122]

[0135] In some embodiments, the conditioned feedstock is preheated using one or more heaters known in the art. This raises the temperature above the decomposition temperature of the catalyst precursor, liberating the catalyst metal therefrom, which can then react with sulfur present in and / or added to the heavy oil feedstock (e.g., as hydrogen sulfide gas) to form active, dispersed metal sulfide catalyst particles in situ within the heavy oil.

[0123]

[0136] FIG. 7A schematically shows an exemplary system 700 for mixing a catalyst precursor 702 with a heavy oil feedstock 708 to form an adjusted feedstock. The catalyst precursor 702 is first mixed with a hydrocarbon oil diluent 704 by a first static in-line low shear mixer 706 to advantageously form a diluted precursor mixture. The catalyst precursor 702 is preferably oil-soluble. The hydrocarbon oil diluent 704 includes one or more high-boiling hydrocarbon materials and optionally one or more medium-boiling materials.

[0124]

[0137] The catalyst precursor composition 702 is advantageously mixed with the hydrocarbon oil diluent 704 at a temperature below the temperature at which a significant portion of the catalyst precursor composition 702 begins to decompose. It is understood that the actual temperature at which the diluted precursor mixture is formed typically depends largely on the decomposition temperature of the particular precursor composition being used. If the hydrocarbon oil diluent 704 is initially too hot, for example above the decomposition temperature of the catalyst precursor 702, it is first passed through a cooler 705 to lower its temperature, for example below the decomposition temperature of the catalyst precursor 702.

[0125]

[0138] The degree of initial mixing achieved within the in-line mixer 706 depends at least in part on the number of stages within the low-shear static in-line mixer. In one embodiment, the mixer 706 is characterized by being included between about 2 and about 20 stages, preferably between about 7 and about 15 stages, more preferably between about 8 and about 12 stages. In mixing theory, each "stage" is substantially equivalent to having a vigorously agitated vessel. Since the mixing is incomplete (i.e., there is some short-circuiting of the vessel by the components being mixed), the degree of mixing is improved when a series of mixing vessels (i.e., stages) are used. An exemplary static in-line mixer 706 does not include moving parts but includes a plurality of internal baffles or other elements inside a pipe or other housing. The internal baffles or other elements direct the fluid flowing in different directions so as to mix the various components by repeatedly dividing and remixing the fluid into turbulent flow. The number of stages of the static in-line mixer correlates empirically to the degree of mixing that can be expected within the static mixer when compared to the degree of mixing that would occur if a series of mixing vessels were used (i.e., the fluid exiting the first vessel enters the second vessel for mixing, the fluid exiting the second vessel enters the third vessel, etc.). In other words, a static in-line mixer characterized by including 10 stages provides a degree of mixing substantially equivalent to that provided by a mixing system including a series of 10 mixing vessels.

[0126]

[0139] Diluting the catalyst precursor with a hydrocarbon diluent prior to mixing with the heavy oil feedstock is useful in achieving a complete blend of the precursor in the heavy oil feedstock because the hydrocarbon oil diluent blends more readily with the heavy oil feedstock than the catalyst precursor alone. It is important that the catalyst precursor be premixed with the hydrocarbon diluent and that care be taken to mix the components for a time sufficient to completely blend the precursor with the feedstock before substantial decomposition of the precursor occurs in the overall process and mixing system.

[0127]

[0140] Advantageously, pre-blending the precursor composition 702 with the hydrocarbon diluent 704 before blending the diluted precursor mixture with the heavy oil feedstock 708 has been found to significantly assist in fully and intimately blending the precursor composition 702 within the feedstock 708. Forming the diluted precursor mixture advantageously (1) reduces or eliminates the solubility difference between the more polar catalyst precursor 702 and the heavy oil feedstock 708, (2) reduces or eliminates the viscosity difference between the catalyst precursor composition 702 and the heavy oil feedstock 708, and / or (3) breaks down the bonds or associations between aggregates of catalyst precursor molecules to form a solute within the hydrocarbon diluent 704 that is much more readily dispersed within the heavy oil feedstock 708, thereby shortening the overall mixing time.

[0128]

[0141] When the heavy oil feedstock 708 contains water (e.g., condensed water), it is particularly advantageous to first form the diluted precursor mixture. Otherwise, the greater affinity of water for the polar catalyst precursor 702 can cause local aggregation of the precursor, resulting in inadequate dispersion and formation of micron-sized or larger catalyst particles. The hydrocarbon diluent 704 preferably contains substantially no water (i.e., contains less than about 0.5% water) and prevents the formation of a substantial amount of micron-sized or larger catalyst particles.

[0129]

[0142] The diluted precursor mixture is then combined with the heavy oil feedstock 708 and mixed for a sufficient time in a manner that disperses the catalyst precursor throughout the feedstock to provide a conditioned feedstock in which the precursor is fully mixed within the heavy oil feedstock. In the illustrated mixing system 700, the heavy oil feedstock 708 and the diluted precursor mixture are blended in a second low-shear, static in-line mixer 710. Similar to the first mixer 706, the second mixer 710 preferably includes between 2 and 20 stages, more preferably between 7 and 15 stages, and most preferably between 8 and 12 stages.

[0130]

[0143] Following the second static in-line mixer 710 is a dynamic high-shear mixer 712 (e.g., a vessel having a propeller or turbine impeller to provide very turbulent high-shear mixing). An example of a suitable dynamic high-shear mixer is an 800LS in-line mixer manufactured by Silverson Machines, Ltd., located in Waterside, England. The mixing time of the static in-line mixer depends on the number of stages and the volumetric flow rate of the components. Increasing the intensity and / or shear energy of the mixing process in the high-shear mixer 712 can reduce the mixing time required to achieve complete mixing of the catalyst precursor 702 in the heavy oil feedstock 708. The mixing time in the static in-line mixer 710 can advantageously comprise the majority of the total mixing time. Such a configuration advantageously uses the pressure drop of the static mixer 710 to achieve a degree of mixing, followed or preceded by additional mixing in the high-shear mixer 712.

[0131]

[0144] Additional equipment may be included downstream in the system 700 to provide additional mixing of the catalyst precursor to achieve high dispersion in the heavy oil feedstock 708. For example, the static in-line mixer 710 and the high-shear mixer 712 (or another mixing configuration) can be followed by a surge tank 714 having a recirculation pump(s), and optionally one or more multi-stage centrifugal pumps and a second surge tank. Further mixing can be performed using a high-energy pump 716 having multiple tanks, in which the catalyst precursor and the heavy oil feedstock are agitated and mixed as part of the pumping process itself used to deliver the conditioned feedstock to the hydrotreating reactor.

[0132]

[0145] By molecular diffusion, the catalyst precursor 702 in the surge tank 714 continues to diffuse more completely throughout the heavy oil feedstock 708. Finally, the conditioned feedstock is pumped from the surge tank 714, through the pump 716, and delivered to the reactor system for hydrotreating of the heavy oil feedstock. As described above, the pump 716 may advantageously include a multi-stage high-pressure pump. For the plurality of compression stages, such a pump results in more intense mixing of the conditioned feedstock and ensures complete mixing of the catalyst precursor 702 in the feedstock 708 if such mixing has not yet been achieved.

[0133]

[0146] FIG. 7B schematically shows another exemplary system 700 for intimately mixing the catalyst precursor 702 with the heavy oil feedstock 708. The catalyst precursor 702 is metered through a metering pump 703 to achieve a desired flow rate. The catalyst precursor 702 is then mixed with the high-boiling hydrocarbon oil diluent 704 in a first static in-line mixer 706 to form a diluted catalyst mixture 707.

[0134]

[0147] The catalyst precursor 702 is mixed with the hydrocarbon oil diluent 704 at a temperature below the temperature at which a significant portion of the catalyst precursor 702 begins to decompose. If the hydrocarbon oil diluent 704 is initially too hot, e.g., above the decomposition temperature of the catalyst precursor 702, it is first passed through a cooler 705 to lower its temperature, e.g., below the decomposition temperature of the catalyst precursor 702. The diluted precursor mixture 707 is then combined with the heavy oil feedstock 708 in a static in-line mixer 710 to form a conditioned feedstock in which the precursor 702 is completely mixed with the heavy oil feedstock 708. In the illustrated system 700, the heavy oil feedstock 708 is split into two streams, 708a and 708b, for progressive mixing with the diluted precursor mixture 707. The partial stream 708b is shown to be added directly to the surge tank 714.

[0135]

[0148] The undiluted precursor mixture 707 is blended with a first heavy oil feed stream 708a in a second low shear static in-line mixer 710. The effluent from mixer 710 contains a mixture of diluent 704, catalyst precursor 702, and a portion of heavy oil feed 708. The effluent is introduced into a dynamic high shear mixer 712 (e.g., a vessel having a propeller or turbine impeller to provide very turbulent high shear mixing) and acts to intimately blend the catalyst precursor and the heavy oil feed. The effluent 713 from high shear mixer 712 is introduced into a surge tank 714 together with any remaining heavy oil feed 708b.

[0136]

[0149] Additional equipment may be included downstream to provide even more complete mixing of the catalyst precursor in the heavy oil feed. For example, a pump-around of surge tank 714 and / or one or more high pressure multi-stage centrifugal pumps may follow the static in-line mixer 710 and high shear mixer 712 (or other mixing configuration). For example, the static in-line mixer 710 and high shear mixer 712 (or another mixing configuration) may be followed by an optional device 715 such as a heated surge tank 714 having a plurality of recirculation pumps (e.g., a plurality of heated surge tanks arranged in parallel or in series) and one or more multi-stage centrifugal pumps and / or a high temperature surge tank. The illustrated system 700 further includes pumps 716a, 716b, 716c arranged in parallel as further discussed below, which can achieve additional mixing.

[0137]

[0150] In the hybrid system 700 of FIG. 7B, only a portion of the heavy oil feedstock 708 (i.e., stream 708a) is initially mixed with the diluent precursor mixture 707. Although the feedstock 708 is shown as being split into two streams 708a and 708b, it is understood that all of the heavy oil feedstock 708 could be added immediately (i.e., there may be no splitting of the feedstock 708), or the feedstock 708 could be split into more streams for progressive blending with the catalyst precursor 702. The conditioned feedstock 713 may be introduced into the surge tank 714 along with any remaining heavy oil feedstock 708b. (For example, optional devices 715 such as one or more heated surge tanks in series or parallel having multiple recirculation pumps, followed by a centrifugal pump and a high-temperature surge tank). The surge tank(s) 714 may be used to more completely disperse the catalyst precursor 702 throughout the heavy oil feedstock 708. The surge tank 714 may provide a residence time between 5 minutes and 60 minutes, or between 10 minutes and 50 minutes, or between 15 minutes and 30 minutes. By diffusion, the catalyst precursor 702 in the surge tank 714 continues to more completely disperse to form a dispersed catalyst throughout the heavy oil feedstock 708 in preparation for heating and decomposition.

[0138]

[0151] Thereafter, the conditioned feedstock is pumped from the surge tank(s) 714 and optional device 715 by pumps 716a, 716b, 716c and delivered to a reactor for hydrotreating the heavy oil feedstock. The pumps 716a, 716b, 716c may include multi-stage high-pressure pumps. When configured using multiple compression stages (e.g., more than about 10), such pumps 716 result in more vigorous mixing of the conditioned feedstock and ensure complete mixing of the catalyst precursor 702 within the feedstock 708. The conditioned feedstock delivered to the hydrotreating reactor contains a catalyst precursor dispersed throughout the heavy oil feedstock to the molecular level, and upon heating and decomposition of the precursor to form the catalyst, the catalyst particles advantageously are colloidal or molecular in size and highly dispersed.

[0139]

[0152] The illustrated embodiment advantageously includes three pumps in parallel (e.g., pumps 716a, 716b, and 716c). Configuring the system so that pumps 716 are in parallel results in an increased flow rate of the conditioned feedstock delivered to the downstream hydroprocessing reactor. In alternative embodiments, the pumps may be positioned in series, or a combination of series and parallel pumps. Placing pumps in series effectively increases the number of intense mixing stages through which the conditioned feedstock passes. For example, two pumps in series, each containing five stages, can be used instead of a single pump containing ten stages to achieve substantially the same intimate mixing of the catalyst precursor within the heavy oil feedstock to provide the conditioned feedstock. In either configuration, the result is that the catalyst precursor is homogeneously dispersed at the colloidal and / or molecular level within the feedstock, resulting in the formation of highly dispersed metal sulfide catalyst particles upon heating.

[0140]

[0153] 8A-8B illustrate a mixing system 800 configured to mix a heavy oil feedstock 802 with a diluted precursor mixture 808. The diluted precursor mixture 808 is formed by mixing a catalyst precursor 804 (e.g., an oil soluble catalyst precursor) with a high boiling point hydrocarbon diluent 806 using one or more mixers known in the art, such as one or more static in-line mixers and / or one or more high shear mixers. The heavy oil feedstock 802 and the diluted precursor mixture 808 are fed into a common feed line 810 and split into first and second parallel mixing lines 812a, 812b.

[0141]

[0154] The heavy oil feedstock side stream 836 can optionally be used as a diluent to make the diluted precursor mixture 808. A cooler 838 can be used to reduce the temperature of the heavy oil feedstock side stream 836 to prevent premature thermal decomposition of the catalyst precursor 804 in the diluted precursor mixture 808 before it is thoroughly mixed with the heavy oil feedstock 802.

[0142]

[0155] Each of the mixing lines 812a, 812b may include upstream valves 814a, 814b, which can be selectively opened during operation of the mixing lines 812a, 812b and closed to take the mixing line 812 offline for maintenance and cleaning. When online, the upstream valves 814a, 814b are opened to allow split flows of the heavy oil feedstock 802 and the diluent precursor mixture 808 to flow through the first and second mixing lines 812a, 812b. In a preferred embodiment, the first and second parallel mixing lines 812a, 812b are designed using symmetrical piping and mixing devices such that the pressure drop is substantially equal through each parallel mixing line 812 and equivalent flow can be maintained between different mixing lines 812. Nevertheless, different capacity and flow mixing lines 812 can be used, for example, when retrofitting a single row of mixing lines to include one or more additional mixing lines.

[0143]

[0156] In the mixing system 800 shown in FIG. 8A, split flows of the heavy oil feedstock 802 and the diluent precursor mixture 808 pass through the first and second static in-line mixers 816a, 816b for initial mixing to produce first and second initial mixed flows, and then through the first and second strainers 818a, 818b to remove any unwanted solids in the initial mixed flows. The first and second mixed flows are then supplied to the first and second high-shear mixers 820a, 820b to provide first and second conditioned feedstock flows. Optional first and second flow meters 822a, 822b can be provided to measure the flow through the first and second mixing lines 812a, 812b downstream of the first and second high-shear mixers 820a, 820b.

[0144]

[0157] FIG. 8B is similar to FIG. 8A, except that a common static in-line mixer 816 is located in the common supply line 810 and functions as a premixer upstream of the point where the first and second parallel mixing lines 812a and 812b branch, and the individual static in-line mixers 816a, 816b in the mixing lines 812a and 812b are omitted.

[0145]

[0158] The first and second flow control devices 824a, 824b are each located downstream of the high shear mixers 820a, 820b. The flow control devices 824a, 824b can provide multifaceted functions. When both the first and second parallel mixing lines 812a, 812b are on-line, the flow control devices 824a, 824b are open. When one of the mixing lines 812 is taken off-line, the corresponding flow control device 824 is closed and can prevent the backflow of the pressurized and adjusted feedstock from the other mixing line 812 still in operation. The flow control device 824 of the mixing line 812 still in operation can be fully open throughout, or alternatively, can be partially closed to restrict the flow and increase the upstream pressure, allowing some of the heavy oil feedstock 802 to enter the bypass line 840 or making it possible.

[0146]

[0159] The adjusted feedstock flows from the first and second mixing lines 812a, 812b are supplied to a common discharge line 825, combined to form a common adjusted feedstock flow 846. The common adjusted feedstock flow 846 passes through a common flow measurement device 828 (e.g., a flow meter) and then through a common flow control device 826 (e.g., a valve), is remixed with any heavy oil feedstock from the bypass line 840, and then enters the surge tank 830.

[0147]

[0160] The adjusted feedstock side stream 832 from the surge tank 830 can optionally be used as a diluent to make the dilution precursor mixture 808. The cooler 834 is used to lower the temperature of the adjusted feedstock side stream 832 to prevent premature thermal decomposition of the catalyst precursor 804 in the dilution precursor mixture 808 before it is fully mixed with the heavy oil feedstock 802.

[0148]

[0161] When both parallel mixing lines 812a and 812b are operating online, the common flow control device 826 is open. When one of the mixing lines 812a, 812b is closed and taken offline, the common flow control device 826 partially closes to restrict the flow of material through the common discharge line 825, increasing the upstream pressure to cause or enable a portion of the heavy oil feedstock to enter the bypass line 840. The common flow control device 826 can be used alone or in combination with one of the flow control devices 824 corresponding to the mixing line 812 that is still in operation.

[0149]

[0162] The bypass line 840 typically does not have the heavy oil feedstock 802 flowing through it when both the first and second mixing lines 812a, 812b are operating online. However, when one of the parallel mixing lines 812 is closed and taken offline, a portion of the heavy oil feedstock 802 not supplied to the remaining online mixing line 812 causes or enables the passage through the bypass line 840 to maintain the throughput of the heavy oil feedstock 802 through the mixing system 800. As discussed above, the flow of the heavy oil feedstock 802 through the bypass line 840 is caused or induced by restricting the flow through the common discharge line 825, partially closing the common flow control valve 826 and / or the mixing line valve 824 of the operating mixing line 812. This induces a pressure drop and increases the upstream pressure sufficient to cause a portion of the heavy oil feedstock 802 to enter the bypass line 840. An optional flow meter 842 in the bypass line 840 measures the flow rate of the heavy oil feedstock 802 passing through the bypass line 840. The bypass line 840 is joined to the common discharge line 825 to combine the heavy oil feedstock 808 from the bypass line with the common regulated feedstock stream 846 downstream of the flow control device 826 and the flow meter 828.

[0150]

[0163] The flow rates of the split heavy oil feedstock streams passing through the remaining operating mixing line 812 and the bypass line 840 can be measured by a common flow meter 828 and optionally a bypass flow meter 842, respectively. The respective flow rates of the materials passing through the remaining operating mixing line 812 and the bypass line 840 can be adjusted by adjusting the common flow control valve 826 and / or the bypass line valve 844. By measuring the flow rate using a flow meter and performing the adjustment using a flow control device, the desired balance of the flow through the various lines can be achieved and maintained. In addition to adjusting the flow rate through the bypass line 840, when the first and second mixing lines 812a, 812b are open and operating, the bypass line valve 844 can be closed or partially restricted to balance the line pressure to ensure that the heavy oil feedstock 802 does not pass through the bypass line 840 in either the forward or reverse direction.

[0151]

[0164] An exemplary method of mixing a catalyst precursor into heavy oil includes using the mixing system 800 illustrated in FIG. 8A, (1) blending a quantity of catalyst precursor 804 with a quantity of diluent 806 to form a pre-dilution precursor mixture 808, (2) using a plurality of parallel mixing lines 812, each parallel mixing line 812 including one or more mixers 816, 820 and at least one valve 814, 824 for adjusting the flow of the mixing line 812, to mix the pre-dilution precursor mixture 808 with the heavy oil feedstock 802 to form a plurality of adjusted feedstock streams, (3) combining the adjusted feedstock streams in a common discharge line 825 downstream of the parallel mixing lines 812 to form a common adjusted feedstock stream 846, (4) stopping the flow through the mixing line 812 and causing or allowing a portion of the heavy oil feedstock 802 to enter the bypass line 840, bypass the parallel mixing lines 812, and combine with the common adjusted feedstock stream 846 in the common discharge line 825, and While a portion of the heavy oil feedstock 802 passes through the bypass line 840, continuing to mix at least a portion of the diluent precursor mixture 808 with the remaining portion of the heavy oil feedstock 802 using at least one other of the parallel mixing lines 812.

[0152]

[0165] When using the alternative mixing system 800 illustrated in FIG. 8B, the method optionally includes premixing the diluent precursor mixture 808 with the heavy oil feedstock 802 using a common static in-line mixer 816 upstream of the point where the first and second mixing lines 812a, 812b branch. This method also omits mixing the diluent precursor mixture 808 with the heavy oil feedstock 802 using the static in-line mixers 816a, 816b of the first and second mixing lines 812a, 812b illustrated in FIG. 8A.

[0153]

[0166] The hydrotreating system may have a defined flow rate of the heavy oil. When operating both the first and second parallel mixing lines 812a, 812b, it may be advantageous or preferable to equally divide the heavy oil feedstock 802 such that there is a symmetric (e.g., equal) flow of material (e.g., half of the defined system flow rate through each mixing line 812a, 812b) through each of the first and second parallel mixing lines 812a, 812b.

[0154]

[0167] When one of the mixing lines 812 is closed and taken offline, the route through which a portion of the heavy oil feedstock passes through the bypass line 840 is changed to maintain the same or a similar defined flow rate of the heavy oil feedstock 802 through the mixing system 800. By way of non-limiting example, for a mixing system 800 having a defined flow rate, the flow rate of the heavy oil feedstock 802 through the bypass line 840 and the remaining online mixing line 812 can be the same (e.g., approximately half of the defined system flow rate through each line). In a preferred embodiment, the flow rate of the heavy oil feedstock 802 through the remaining online mixing line 812 is increased to more than half of the defined flow rate, and the flow rate of the heavy oil feedstock 802 through the bypass line 840 is decreased to less than half of the defined flow rate.

[0155]

[0168] Alternatively, it is possible to make the flow rate of the heavy oil feedstock 802 through the bypass line 840 greater than the flow rate through the remaining on-line mixing lines 812. For example, the flow rate through the bypass line 840 exceeds half of the defined system flow rate. To maintain the same or similar flow rate of the heavy oil feedstock through the system, the corresponding flow rate through the remaining on-line mixing lines 812 can be reduced to less than half of the defined system flow rate.

[0156]

[0169] When the heavy oil feedstock side stream 836 is used as a diluent to make the diluted precursor mixture 808 and the flow rate of the heavy oil feedstock 802 through the mixing system 800 is about 100 tons per hour, the amount of the heavy oil feedstock side stream 836 can be up to about 10 tons per hour, or up to about 5 tons per hour (or between about 0 to 10 tons per hour or about 0 to 5 tons per hour depending on the conditions within the mixing system 500). When the flow rate of the heavy oil feedstock 802 through the mixing system 800 is less than 100 tons per hour or more than 100 tons per hour, the flow rate of the heavy oil feedstock side stream 836 used as a diluent to make the diluted precursor mixture 808 can be up to about 10% of the total flow, or about 5% (or between about 0.1 to 10% of the total flow or about 0.5 to 5% depending on the conditions within the mixing system 800).

[0157]

[0170] The adjusted feedstock sidestream 832 is used as a diluent to make the diluted precursor mixture 808, and when the flow rate of the heavy oil feedstock 802 through the mixing system 800 is about 100 tons per hour, the amount of the adjusted feedstock sidestream 832 can be up to about 10 tons per hour, or up to about 5 tons per hour (or between about 0 to 10 tons per hour or about 0 to 5 tons per hour depending on the conditions within the mixing system 800). When the flow rate of the heavy oil feedstock 802 through the mixing system 800 is less than 100 tons per hour or more than 100 tons per hour, the flow rate of the adjusted feedstock sidestream 832, which is used as a diluent to make the diluted precursor mixture 808, can be up to about 10% of the total flow, or about 5% (or between about 0.1 to 10% of the total flow or about 0.5 to 5% depending on the conditions within the mixing system 800).

[0158]

[0171] In some embodiments, the dispersed metal sulfide catalyst particles are formed in-situ within the entirety of the heavy oil added to the hydrotreating reactor. This can be achieved by first using the mixing methods and systems of the present disclosure to mix a catalyst precursor with a diluent that forms a diluted precursor mixture, which is then mixed with the entirety of the heavy oil in a plurality of parallel mixing lines to form parallel adjusted feedstock streams, and the parallel adjusted feedstock streams are combined with a periodic heavy oil feedstock from a bypass line into a common adjusted feedstock stream, which is then heated to decompose the catalyst precursor and cause or enable a reaction of the catalyst metal with sulfur and / or sulfur-containing molecules in and / or added to the heavy oil to form the dispersed metal sulfide catalyst particles in-situ.

[0159]

[0172] The catalyst precursor may be oil-soluble and can have a decomposition temperature in the range of about 100°C to about 350°C, or in the range of about 150°C to about 300°C, or in the range of about 175°C to about 250°C. Examples of catalyst precursors include organometallic complexes or compounds, more specifically, oil-soluble compounds or complexes of transition metals and organic acids that have a decomposition temperature or range high enough to avoid substantial decomposition when mixed with the heavy oil feedstock under suitable mixing conditions. When mixing the catalyst precursor with a hydrocarbon oil diluent, it is advantageous to maintain the diluent below the temperature at which significant decomposition of the catalyst precursor occurs. One of ordinary skill in the art selects a mixing temperature profile that results in intimate mixing of the selected precursor composition without substantial decomposition prior to the in-situ formation of the dispersed metal sulfide catalyst particles.

[0160]

[0173] Examples of catalyst precursors include, but are not limited to, molybdenum diethylhexanoate, molybdenum octoate, molybdenum naphthenate, vanadium naphthenate, vanadium octoate, molybdenum hexacarbonyl, vanadium hexacarbonyl, and pentacarbonyl iron. Other catalyst precursors include molybdenum salts containing a plurality of cationic molybdenum atoms and a plurality of carboxylic acid anions having at least 8 carbon atoms, which are at least one of (a) aromatic, (b) alicyclic, or (c) branched, unsaturated, and aliphatic. By way of example, each carboxylic acid anion can have 8 to 17 carbon atoms, or 11 to 15 carbon atoms. Examples of carboxylic acid anions that conform to at least one of the foregoing categories include carboxylic acid anions derived from carboxylic acids selected from the group consisting of 3-cyclopentylpropionic acid, cyclohexanebutanoic acid, biphenyl-2-carboxylic acid, 4-heptylbenzoic acid, 5-phenylvaleric acid, geranic acid (3,7-dimethyl-2,6-octadienoic acid), and combinations thereof.

[0161]

[0174] In other embodiments, carboxylic acid anions suitable for use in the preparation of oil-soluble and thermally stable molybdenum catalyst precursor compounds are derived from carboxylic acids selected from the group consisting of 3-cyclopentylpropionic acid, cyclohexanebutanoic acid, biphenyl-2-carboxylic acid, 4-heptylbenzoic acid, 5-phenylvaleric acid, geranic acid (3,7-dimethyl-2,6-octadienoic acid), 10-undecenoic acid, dodecanoic acid, and combinations thereof. Molybdenum catalyst precursors prepared using carboxylic acid anions derived from the aforementioned carboxylic acids have been found to have improved thermal stability.

[0162]

[0175] Catalyst precursors with high thermal stability can have a first decomposition temperature above 210 °C, above about 225 °C, above about 230 °C, above about 240 °C, above about 275 °C, or above about 290 °C. Such catalyst precursors can have a peak decomposition temperature above 250 °C, or above about 260 °C, or above about 270 °C, or above about 280 °C, or above about 290 °C, or above about 330 °C.

[0163]

[0176] In the case of heavy oil feedstocks that are solid at room temperature or extremely viscous, such feedstocks can advantageously be heated to produce a softened feedstock with a sufficiently low viscosity so that the oil-soluble catalyst precursor can be well mixed into the feedstock. Generally, reducing the viscosity of the heavy oil feedstock reduces the time required to achieve complete and intimate mixing of the oil-soluble precursor composition within the feedstock. However, it can also cause premature decomposition of the catalyst precursor. A catalyst precursor with a decomposition temperature suitable for a given heavy oil feedstock can be selected.

[0164]

[0177] After the catalyst precursor is well mixed throughout the heavy oil to obtain a conditioned feedstock, the composition is heated to cause decomposition of the catalyst precursor, thereby liberating the catalyst metal, causing or enabling the reaction of the catalyst metal with sulfur in the heavy oil and / or sulfur added to the heavy oil, and forming in-situ active metal sulfide catalyst particles. The metal from the catalyst precursor can first form a metal oxide and then react with sulfur in the heavy oil to obtain a metal sulfide compound that forms the final active catalyst. If the heavy oil contains sufficient or excess sulfur, the final activated catalyst may be formed in-situ by heating the feedstock to a temperature sufficient to liberate sulfur from the feedstock. In some cases, sulfur can be liberated at the same temperature at which the precursor composition decomposes. In other cases, further heating to a higher temperature may be required. Hydrogen sulfide gas can be added to heavy oils that lack sufficient sulfur to form the active metal sulfide catalyst particles.

[0165]

[0178] When the catalyst precursor is completely mixed throughout the heavy oil, at least a significant portion of the free metal ions are sufficiently protected or shielded from other metal ions, resulting in the formation of a molecularly dispersed catalyst when reacting with sulfur to form a metal sulfide compound. Under some circumstances, slight aggregation may occur, and colloidal-sized catalyst particles may be obtained. However, by taking care to completely mix the catalyst precursor throughout the feedstock prior to thermal decomposition of the catalyst precursor, it is believed that individual catalyst molecules rather than colloidal particles can be obtained. If simply blended without being well mixed, the catalyst precursor containing the feedstock typically causes the formation of large aggregated metal sulfide compounds larger than micrometer size.

[0166]

[0179] To form the dispersed metal sulfide catalyst particles, the conditioned feedstock is heated to a temperature in the range of about 275 °C (527 °F) to about 450 °C (842 °F), or in the range of about 310 °C (590 °F) to about 430 °C (806 °F), or in the range of about 330 °C (626 °F) to about 410 °C (770 °F).

[0167]

[0180] The concentration of catalytic metal brought about by dispersed metal sulfide catalyst particles in heavy oil can depend on the type of reactor being used. When the dispersed metal sulfide catalyst is used together with a solid supported catalyst (e.g., a fluidized bed reactor or a fixed bed reactor), the concentration may be in the range of about 1 weight ppm to about 150 weight ppm of the heavy oil and any diluent, or in the range of about 5 weight ppm to about 95 weight ppm, or in the range of about 10 weight ppm to about 75 weight ppm. When the dispersed metal sulfide catalyst is the only catalyst being used (e.g., a slurry reactor), the concentration is typically higher, e.g., in the range of about 30 weight ppm to about 1000 weight ppm of the heavy oil and any diluent, in the range of about 50 weight ppm to about 500 weight ppm, or in the range of about 75 weight ppm to about 300 weight ppm.

[0168]

[0181] When the heavy oil contains significant amounts of asphaltene molecules, the dispersed metal sulfide catalyst particles can preferentially associate with or remain in close proximity to the asphaltene molecules. Asphaltene molecules are generally more hydrophilic and less hydrophobic than other hydrocarbons contained in heavy oil, so asphaltene molecules can have a higher affinity for the metal sulfide catalyst particles. Since the metal sulfide catalyst particles tend to be hydrophilic, individual particles or molecules tend to move towards the more hydrophilic parts or molecules within the heavy oil.

[0169]

[0182] The very highly polar nature of the metal sulfide catalyst particles causes or allows association with the asphaltene molecules, but generally there is incompatibility between the very highly polar catalyst compounds and the hydrophobic heavy oil, requiring the aforementioned intimate or complete mixing of the catalyst precursors in the feedstock prior to the decomposition and in-situ formation of the active catalyst particles. Since the metal catalyst compounds are very highly polar, they cannot be effectively dispersed in the heavy oil if added directly. In practice, by forming smaller active catalyst particles, a number of catalyst particles are produced that provide catalytic sites more uniformly distributed throughout the heavy oil. Also, it increases the catalyst surface area.

[0170]

[0183] Complete mixing of the catalyst precursor with the heavy oil feedstock before thermal decomposition of the catalyst precursor and formation of the dispersed metal sulfide catalyst particles substantially reduces the fouling rate of the apparatus, and the fouling rate of the apparatus can be measured by at least one of (i) the frequency of heat exchanger cleaning required, (ii) the frequency of switching to a preheat exchanger, (iii) the frequency of filter replacement, (iv) the frequency of strainer cleaning or replacement, (v) the rate of decrease in the surface temperature of the apparatus, including within the apparatus selected from a heat exchanger, a separator, or a distillation column, (vi) the rate of increase in the metal temperature of the furnace tubes, (vii) the rate of increase in the calculated fouling resistance factor of the heat exchanger and the furnace, (viii) the rate of increase in the differential pressure of the heat exchanger, (ix) the cleaning frequency of the atmospheric distillation column and / or the vacuum distillation column, or (x) the frequency of regular maintenance.

Example

[0171] V. Example Comparative Example 1

[0184] Molybdenum 2-ethylhexanoate having a decomposition temperature of about 150 °C is used as an oil-soluble catalyst precursor in the heavy oil feedstock. The catalyst precursor is added directly to the feed line for the heavy oil feedstock before feeding the heavy oil feedstock into a fluidized bed reactor containing a heterogeneous fluidized bed catalyst. The heavy oil feedstock is at a temperature of about 200 °C at the time of addition of the catalyst precursor, and no mixing device is used before feeding the heavy oil feedstock into the hydrotreating reactor.

[0172]

[0185] The catalyst precursor thermally decomposes to form metal catalyst aggregates having a size of 1 to 300 μm. The catalyst aggregates have a small surface area and low catalytic activity. They do not enhance the performance of the fluidized bed reactor but cause additional fouling and precipitate formation.

[0173] Comparative Example 2

[0186] This example is similar to Example 1, except that a series of mixers including a static in-line mixer and a high-shear mixer and following a surge tank and a pressurized pump are used to mix the catalyst precursor with the heavy oil feedstock. The catalyst precursor is mixed into the heavy oil feedstock, but it thermally decomposes before proper mixing occurs, resulting in the formation of larger catalyst particles with sizes ranging from 1 to 150 μm. The catalyst particles have a small surface area and low catalytic activity. They do not enhance the performance of the fluidized bed reactor, but rather cause additional fouling and precipitate formation.

[0174] Comparative Example 3

[0187] Rather than directly mixing the catalyst precursor into the bulk of the heavy oil feedstock, first a sidestream of the heavy oil feedstock (5 vol%) is pre-mixed with it as a diluent to form a pre-diluted precursor mixture, and then it is mixed into the remainder (95 vol%) of the heavy oil feedstock. Since the sidestream of the heavy oil feedstock is at a temperature higher than the decomposition temperature of the catalyst precursor, the catalyst precursor thermally decomposes before it can be properly mixed throughout the diluent, resulting in the formation of larger catalyst particles with sizes ranging from 1 to 150 μm. The catalyst particles have a small surface area and low catalytic activity. They do not enhance the performance of the fluidized bed reactor, but rather cause additional fouling and precipitate formation.

[0175] Comparative Example 4

[0188] Rather than directly mixing the catalyst precursor into the heavy oil feedstock, first it is pre-mixed with a middle-boiling hydrocarbon to form a pre-diluted precursor mixture at a temperature lower than its decomposition temperature. Then, the pre-diluted precursor mixture is mixed into the heavy oil feedstock to form an adjusted feedstock, which is then heated to decompose the catalyst precursor and form active metal sulfide catalyst particles in-situ. The resulting dispersed metal sulfide catalyst particles have sizes less than 1 μm and good catalytic activity. However, the process of forming the pre-diluted precursor mixture requires the use of expensive hydrocarbon materials, and such hydrocarbon materials are either in short supply, required for other processes at the refinery, or sold at a price that is uneconomical for use as a diluent for the catalyst precursor.

[0176] Example 5

[0189] Rather than pre - mixing the catalyst precursor with a medium - boiling hydrocarbon to form a diluted precursor mixture, instead, a sidestream of the heavy oil feedstock (5% by volume) as a diluent is pre - mixed with the catalyst precursor to form a diluted precursor mixture, and then this is mixed into the remainder (95% by volume) of the heavy oil feedstock. Before mixing with the catalyst precursor, the heavy oil feedstock sidestream is cooled to a temperature of 150 °C, which is close to the decomposition temperature of the catalyst precursor, and thus does not cause more than 20% decomposition of the catalyst precursor before completely mixing it throughout the diluent.

[0177]

[0190] The diluted precursor mixture is mixed into the heavy oil feedstock to form an adjusted feedstock, and then the adjusted feedstock is heated to decompose the catalyst precursor, forming active metal sulfide catalyst particles in - situ. Most of the dispersed metal sulfide catalyst particles have a size of less than 1 μm and have good catalytic activity.

[0178] Example 6

[0191] This example is the same as Example 5, except that before mixing with the catalyst precursor, the heavy oil feedstock sidestream is cooled to a temperature of 125 °C, which is somewhat lower than the decomposition temperature of the catalyst precursor, and thus does not cause more than 5% decomposition of the catalyst precursor before completely mixing it throughout the diluent.

[0179]

[0192] The diluted precursor mixture is mixed into the heavy oil feedstock to form an adjusted feedstock, and then the adjusted feedstock is heated to decompose the catalyst precursor, forming active metal sulfide catalyst particles in - situ. The dispersed metal sulfide catalyst particles have a size of less than 1 μm and have excellent catalytic activity.

[0180] Example 7

[0193] This example is the same as Examples 5 and 6, except that before mixing with the catalyst precursor, the heavy oil feedstock sidestream is cooled to a temperature in the range of 75 - 95 °C, which is sufficiently lower than the decomposition temperature of the catalyst precursor, and thus does not cause significant decomposition of the catalyst precursor before completely mixing it throughout the diluent.

[0181]

[0194] The diluted precursor mixture is mixed with the heavy oil feedstock to form a prepared feedstock, and then the prepared feedstock is heated to decompose the catalyst precursor to form the active metal sulfide catalyst particles in-situ. The dispersed metal sulfide catalyst particles have a size of less than 1 μm and excellent catalytic activity.

[0182] Example 8

[0195] This example is the same as Example 7, except that a side stream of the heavy oil feedstock adjusted as a high-boiling hydrocarbon diluent is used. The side stream of the adjusted heavy oil feedstock has a temperature of about 225 °C. Before mixing with the catalyst precursor, the adjusted feedstock side stream is cooled to a temperature of 75 - 95 °C, which is well below the decomposition temperature of the catalyst precursor and thus does not cause significant decomposition of the catalyst precursor before it is thoroughly mixed throughout the diluent.

[0183]

[0196] The diluted precursor mixture is mixed with the heavy oil feedstock to form a prepared feedstock, and then the prepared feedstock is heated to decompose the catalyst precursor to form the active metal sulfide catalyst particles in-situ. The dispersed metal sulfide catalyst particles have a size of less than 1 μm and excellent catalytic activity.

[0184] Example 9

[0197] This example is the same as Examples 7 and 8, except that a vacuum tower bottom product is used as the high-boiling hydrocarbon diluent. The vacuum tower bottom product initially has a temperature of about 250 °C. Before mixing with the catalyst precursor, the vacuum tower bottom product is cooled to a temperature of 75 - 95 °C, which is well below the decomposition temperature of the catalyst precursor and thus does not cause significant decomposition of the catalyst precursor before it is thoroughly mixed throughout the diluent.

[0185]

[0198] The diluted precursor mixture is mixed with the heavy oil feedstock to form a prepared feedstock, and then the prepared feedstock is heated to decompose the catalyst precursor to form the active metal sulfide catalyst particles in-situ. The dispersed metal sulfide catalyst particles have a size of less than 1 μm and excellent catalytic activity.

[0186] Example 10

[0199] This example is the same as Examples 7 to 9, except that a deasphalted oil product is used as the high-boiling hydrocarbon diluent. The deasphalted oil product initially has a temperature of about 200°C. Before mixing with the catalyst precursor, the deasphalted oil product is cooled to a temperature of 75 to 95°C, which is well below the decomposition temperature of the catalyst precursor and thus does not cause significant decomposition of the catalyst precursor before it is thoroughly mixed throughout the diluent.

[0187]

[0200] The diluted precursor mixture is mixed with the heavy oil feedstock to form an adjusted feedstock, and then the adjusted feedstock is heated to decompose the catalyst precursor to form the active metal sulfide catalyst particles in-situ. The dispersed metal sulfide catalyst particles are less than 1 μm in size and have excellent catalytic activity.

[0188] Example 11

[0201] This example is the same as Examples 7 to 10, except that a certain amount of medium-boiling hydrocarbon material is used together with the high-boiling hydrocarbon material to form a high-boiling hydrocarbon diluent mixture. Before mixing with the catalyst precursor, the high-boiling hydrocarbon material is cooled to a temperature of 75 to 95°C, which is well below the decomposition temperature of the catalyst precursor and thus does not cause significant decomposition of the catalyst precursor before it is thoroughly mixed throughout the diluent.

[0189]

[0202] The diluted precursor mixture is mixed with the heavy oil feedstock to form an adjusted feedstock, and then the adjusted feedstock is heated to decompose the catalyst precursor to form the active metal sulfide catalyst particles in-situ. The dispersed metal sulfide catalyst particles are less than 1 μm in size and have excellent catalytic activity.

[0190]

[0203] The present invention can be implemented in other specific forms without departing from its gist or essential features. The described embodiments should be considered illustrative in all respects and not restrictive. Therefore, the scope of the present invention is shown not by the above description but by the appended claims. All changes within the meaning and equivalent scope of the claims are included within this scope.

Claims

1. 1. A method for mixing a catalyst precursor with heavy oil, comprising: providing a catalyst precursor having a decomposition temperature; providing a high-boiling hydrocarbon diluent comprised of one or more high-boiling hydrocarbons and optionally one or more intermediate-boiling hydrocarbons, the high-boiling hydrocarbon diluent initially having a temperature above the decomposition temperature of said catalyst precursor; cooling the high-boiling hydrocarbon diluent to a temperature below the decomposition temperature of the catalyst precursor; mixing the catalyst precursor with the high-boiling hydrocarbon diluent to form a diluted precursor mixture; mixing the diluted precursor mixture with the heavy oil feedstock to form a conditioned feedstock.

2. 10. The method of claim 1, wherein the catalyst precursor has a decomposition temperature in the range of about 150°C to about 200°C, and prior to combining the catalyst precursor with the high-boiling hydrocarbon diluent, the high-boiling hydrocarbon diluent is cooled to a temperature below 150°C, or in the range of about 75°C to about 150°C, or in the range of about 75°C to about 125°C, or in the range of about 75°C to about 95°C.

3. 10. The method of claim 1, wherein the catalyst precursor has a decomposition temperature in the range of about 125°C to about 150°C, and prior to combining the catalyst precursor with the high-boiling hydrocarbon diluent, the high-boiling hydrocarbon diluent is cooled to a temperature below 125°C, or in the range of about 75°C to about 125°C, or in the range of about 75°C to about 95°C.

4. The method of claim 1 , wherein the high-boiling hydrocarbon diluent comprises a portion of the heavy oil feedstock.

5. The method of claim 1 , wherein the high-boiling hydrocarbon diluent comprises a portion of the conditioned feedstock.

6. 10. The method of claim 1, wherein the high-boiling hydrocarbon diluent comprises a vacuum tower bottoms product, e.g., recycled vacuum tower bottoms from one or more hydrotreating reactors that hydrotreat the conditioned feedstock or its conversion products.

7. The method of claim 1 , wherein the high-boiling hydrocarbon diluent comprises a deasphalted oil product.

8. The method of claim 1 , wherein the high-boiling hydrocarbon diluent comprises a thermal conversion product such as visbreaker bottoms.

9. 10. The method of claim 1, wherein the high-boiling hydrocarbon diluent has a boiling point of at least about 350°C, or at least about 400°C, or at least about 450°C, or at least about 500°C, or at least about 524°C.

10. 10. The method of claim 1, wherein a portion of the high-boiling hydrocarbon diluent comprises a medium-boiling hydrocarbon material having a boiling point in the range of about 200°C to about 524°C.

11. 11. The method of claim 10, wherein the intermediate boiling hydrocarbon material comprises at least one of vacuum gas oil, decant oil, cycle oil, or atmospheric gas oil.

12. 10. The method of claim 1, wherein the catalyst precursor and boiling hydrocarbon diluent are mixed using one or more static in-line mixers and optionally one or more high shear mixers.

13. The method of claim 1 , wherein the diluted precursor mixture and heavy oil feedstock are mixed using one or more static in-line mixers and one or more high shear mixers.

14. The method of claim 1 further comprising feeding the conditioned feedstock to a surge tank.

15. 10. The method of claim 1, further comprising heating the conditioned feedstock to cause at least a portion of the catalyst precursor to thermally decompose and react with sulfur to form dispersed catalytic sulfide particles in situ within the heavy oil feedstock.

16. A system for mixing a catalyst precursor into heavy oil, the system comprising means for carrying out the method of any one of claims 1 to 15.

17. 1. A system for mixing a catalyst precursor into a heavy oil feedstock, comprising: a catalyst precursor supply line for providing the catalyst precursor at a temperature below the decomposition temperature of the catalyst precursor; at least one diluent feed line providing a high-boiling hydrocarbon diluent comprised of one or more high-boiling hydrocarbons and optionally one or more intermediate-boiling hydrocarbons at an initial temperature above the decomposition temperature of said catalyst precursor; at least one cooler configured to cool the high-boiling hydrocarbon diluent to a temperature below the decomposition temperature of the catalyst precursor; at least one premixer configured to receive and blend the catalyst precursor with the high-boiling hydrocarbon diluent to form a diluted precursor mixture; at least one mixer configured to mix the diluted precursor mixture with the heavy oil feedstock to form a conditioned feedstock.

18. The system of claim 17 , wherein the at least one diluent supply line is configured to provide a side stream of the heavy oil feedstock.

19. The system of claim 17 , wherein the at least one diluent supply line is configured to provide a side stream of the conditioned feedstock.

20. 20. The system of claim 17, wherein the at least one diluent supply line is configured to provide a vacuum tower bottoms product.

21. The system of claim 17 , wherein the at least one premixer comprises at least one static in-line mixer.

22. 20. The system of claim 17, wherein the at least one mixer comprises at least one high shear mixer and optionally a static in-line mixer and / or a strainer.

23. 20. The system of claim 17, further comprising a surge tank configured to receive the conditioned feedstock and to cause or allow further mixing of the catalyst precursor throughout the heavy oil feedstock.

24. 20. The system of claim 17, further comprising a heater configured to heat the conditioned feedstock to cause at least a portion of the catalyst precursor to thermally decompose and react with sulfur to form dispersed catalytic sulfide particles in situ within the heavy oil feedstock.

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