WO2019209525A1 - Methods for assessing heavy oil reactivity - Google Patents

Abstract

A process is provided for determining the suitability of a heavy oil, such as steam cracker tar, for upgrading using hydroprocessing without long term fouling of the hydroprocessing reactor. The process includes introducing a hydrogen donor solvent to a sample of the heavy oil, heating the sample of the tar, quenching the sample, and measuring an amount of dehydrogenated hydrogen donor solvent in the sample. A pyrolysis tar can be blended with a second pyrolysis tar having a low activity reactive radical content to produce a blend that can be hydroprocessed with decreased fouling.

Description

METHODS FOR ASSESSING HEAVY OIL REACTIVITY

INVENTORS: Xurui Zhang, Zhenyu Liu, Zezhou Chen, Teng Xu, Qingya Liu

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This invention claims priority to and the benefit of USSN 62/662,973, filed April

26, 2018 which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present disclosure provides methods for assessing heavy oil reactivity. In particular, the present disclosure includes methods for assessing heavy oil reactivity and determining treatment conditions of a heavy hydrocarbon conversion process.

BACKGROUND

[0003] Hydroprocessing heavy hydrocarbons such as steam cracked tar involves heating the material during the various hydroprocessing steps to temperatures greater than 250°C. For example, during the hydrotreatment stage, the temperature can be 350°C or higher in order to facilitate the addition of hydrogen to reduce levels of sulfur, nitrogen and saturated hydrocarbons. However, tar is very reactive because of the levels of unsaturated hydrocarbons (and radicals formed therefrom), some of which are more reactive than others, present in the heavy feed. Without proper management, hydroprocessing of heavy hydrocarbons can lead to rapid reactor fouling at temperatures as low as 250°C. Hence, depending upon tar reactivity, extensive pretreating processes are performed prior to hydroprocessing.

[0004] Currently, bromine number (BN) is used as an indicator of total olefins content. However, some of the unsaturated molecules present in the heavy hydrocarbons are more reactive than others, e.g., very reactive ones such as vinyl aromatics vs. much less reactive ones such as hexenes. Without being bound by theory, it is believed that the more reactive hydrocarbons are predominantly responsible for reactor fouling. Furthermore, BN cannot distinguish between relative radical reactivities, /._<?., it is a nonselective determination.

[0005] Electron spin resonance (ESR) or electron paramagnetic resonance (EPR) has also been used to quantify radicals. However, the radicals detected by ESR/EPR are radicals survived from the cracking reaction and having a long life span. These radicals are not reactive and therefore termed as“stable radicals” to distinguish from reactive radicals.

[0006] The lack of an accurate reactivity determination means that the level of pretreatment is often more than what is necessary for heavy hydrocarbons that contain more nonreactive unsaturates, which on a large scale becomes very expensive for manufacturers. Therefore, there is a need for methods for assessing radical content of heavy oils, such as tar, in order to determine the level of heavy oil pretreatment, e.g. pretreatment necessary prior to hydroprocessing of tar.

SUMMARY

[0007] When hydroprocessing pyrolysis tars, for example those having an incompatibility number (IN) > 1 10, it has been discovered that using a pyrolysis tar having a desired radical content profile beneficially reduces reactor fouling. More particularly, it has been found that for a wide range of desirable pyrolysis tar hydroprocessing conditions, an amount of reactive radicals (NRR), an amount of high activity reactive radicals (NRR-HA), and/or an amount of low activity reactive radicals (NRR-LA) can be determined for a suitably-prepared pyrolysis tar sample. If the tar is determined to be highly reactive, the tar can be blended or sent away. Furthermore, if the tar is not highly reactive, then the tar can be further processed, e.g. hydroprocessed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0009] FIG. 1 is a process flow diagram illustrating a solvent assisted tar conversion process, according to one embodiment.

[0010] FIG. 2 is ¹³C NMR spectra of oils, according to one embodiment.

[0011] FIG. 3 is HPLC chromatograms of the cracking product of Oil-l at 350°C for 5 min in the presence of DHA or THN, according to one embodiment.

[0012] FIG. 4 is a graph illustrating stable radicals versus heating time of oils, according to one embodiment.

[0013] FIG. 5 A is a graph illustrating stable radicals versus reactive radicals of Oil-l, according to an embodiment.

[0014] FIG. 5B is a graph illustrating stable radicals versus reactive radicals of Oil-2, according to an embodiment.

DETAILED DESCRIPTION

[0015] The present disclosure provides methods for assessing tar reactivity. In at least one embodiment, the present disclosure is directed to methods for determining radical content in a heavy oil (such as a tar) by contacting a heavy oil with hydrogen donor solvents (HDSs) to produce an oil-solvent mixture, and measuring an amount of dehydrogenated hydrogen donor solvent (DHDS). Methods include contacting a second portion of the heavy oil with a second HDS that is different from the first HDS, and measuring an amount of second DHDS. Contacting a heavy oil with an HDS of the present disclosure can capture reactive free radicals formed at high temperatures during tar conversion processes, such as heat soaking. Methods of the present disclosure can provide quantification of the tar reactivity by using HDSs to capture reactive free radicals formed at high temperatures. In at least one embodiment, the method quantifies the reactive radicals generated in thermal cracking of heavy oils from 250°C to 400°C using HDSs having different C-H bond dissociation energies. Methods of the present disclosure can distinguish between low activity and high activity radicals present in a heavy oil and can test for these radicals under hydroprocessing conditions, as compared to detecting room temperature stable radicals by conventional ESR methods.

[0016] As used herein,“heavy oil” can include a pyrolysis tar, an atmospheric residue, a vacuum residue, a coal tar, a biomass tar, or mixtures thereof.

[0017] As used herein, a“low activity radical” is a radical detectable by a HDS having a bond dissociation energy is 330 kJ/mol or lower.

[0018] As used herein, a“high activity radical” is a radical detectable by a HDS having a bond dissociation energy of greater than 330 kJ/mol. Such high activity radicals are reactive towards the second HDS’s described herein.

[0019] As used herein the total amount of“reactive radicals” is equivalent to the low and high activity radicals combined. These reactive radicals are reactive towards the first HDS’s described herein. Also, as used herein, bond dissociation energy is the standard enthalpy change when a bond is homolytically cleaved by homolysis, with reactants and products of the homolysis reaction at a temperature of 0° K.

[0020] In at least one embodiment, a pyrolysis tar at a temperature Ti of 350°C or less is evaluated for its potential for fouling the reactor at desired hydroprocessing conditions. The evaluation is undertaken by sampling the pyrolysis tar, adding a“first HDS” to the pyrolysis tar sample, raising the temperature of the sample to a predetermined temperature T₂ that is at least l0°C greater than Ti, for a predetermined period of time t_h. Typically, T₂ is substantially the same as the desired hydroprocessing temperature, and t_h is substantially the same as the time during which the tar is exposed to hydroprocessing conditions. Following this, the sample is cooled to a temperature T₃ < Ti, and an amount of DHDS is measured to determine an amount of“reactive radicals” (NRR) (mmol radicals/g-oil). If a tar has an NRR value of 0.5 mmol/g-oil or less in 10 minutes at 400°C, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking). Alternatively, a tar having an NRR value of greater than 0.5 mmol/g-oil in 10 minutes at 400°C may be blended with a second pyrolysis tar and/or utility fluid to reduce the free radical content of the blended tar for hydroprocessing.

[0021] A second portion (second sample) of the pyrolysis tar at a temperature T₄ of 350°C or less is then sampled, a“second HDS” (different from the first HDS) is added to the sample, the temperature of the sample is raised to temperature T5 for period of time t_h2. Following this, the sample is cooled to temperature T₆, and the amount of second DHDS is measured to determine an amount of“high activity radicals” NRR-HA (mmol radicals/g-oil).

[0022] In at least one embodiment, T₂ = T5 and t_h = t_h2. Here and throughout the specification and claims, lower case “t” refers to time, and upper case “T” refers to temperature. In at least one embodiment, T3 = Te. If a tar has an NRR-HA value of 0.2 mmol/g- oil or less in 10 minutes at 400°C, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking). Alternatively, a tar having an NRR-HA value of greater than 0.2 mmol/g-oil in 10 minutes at 400°C may be blended with a second pyrolysis tar and/or utility fluid to reduce the free radical content of the blended tar for hydroprocessing.

[0023] The amount of low activity radicals (NRR-LA) is then determined by subtracting the amount of NRR-HA) from (NRR). If a tar has an NRR-LA value of 0.15 mmol/g-oil or less in 10 minutes at 400°C, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking). Alternatively, a tar having an NRR-LA value of greater than 0.15 mmol/g-oil in 10 minutes at 400°C may be blended with a second pyrolysis tar and/or utility fluid to reduce the free radical content of the blended tar for hydroprocessing.

[0024] A stable radical content N_SR of a cooled sample can also be measured, e.g., using ESR.

[0025] A plurality of pyrolysis tars, including a plurality of SCTs, may be blended prior to hydroprocessing to produce a blended pyrolysis tar with a specific free radical profile, e.g., one exhibiting a blended sample N_{TBI IKI} £ a desired N value (NRR, NRR-HA, and/or NRR-LA). Further, the SCTs or pyrolysis tars (or blends thereof) may be combined with a utility fluid for hydroprocessing.

[0026] The following terms are defined for this description and appended claims.

[0027] The term“pyrolysis tar” means a mixture of (a) hydrocarbons having one or more aromatic components and optionally (b) non-aromatic and/or non-hydrocarbon molecules, the mixture being derived from hydrocarbon pyrolysis, with at least 70% of the mixture having a boiling point at atmospheric pressure that is about 550°F (290°C) or greater. Certain pyrolysis tars have an initial boiling point of 200 °C or greater. For certain pyrolysis tars, 90 wt% or greater of the pyrolysis tar has a boiling point at atmospheric pressure of 550°F (290°C) or greater. Pyrolysis tar can comprise, e.g., 50 wt % or greater, e.g., 75 wt % or greater, such as 90 wt % or greater, based on the weight of the pyrolysis tar, of hydrocarbon molecules (including mixtures and aggregates thereof) having (i) one or more aromatic components, and (ii) a number of carbon atoms of about 15 or greater. Pyrolysis tar generally has a metals content of 1.0 x 10³ ppmw or less, based on the weight of the pyrolysis tar, which is an amount of metals that is far less than that found in crude oil (or crude oil components) of the same average viscosity.

[0028] As used herein,“steam cracking tar” (“SCT”) means pyrolysis tar obtained from steam cracking.

[0029] “Tar Heavies” (TH) are a product of hydrocarbon pyrolysis having an atmospheric boiling point of 565°C or greater and comprising 5 wt% or greater of molecules having a plurality of aromatic cores based on the weight of the product. The TH are typically solid at 25°C and generally include the fraction of SCT that is not soluble in a 5:1 (vol.:vol.) ratio of n-pentane: SCT at 25°C. TH generally includes asphaltenes and other high molecular weight molecules.

[0030] Aspects of the present disclosure include (i) obtaining a sample of a pyrolysis tar, (ii) measuring NRR of a suitably-prepared sample of the pyrolysis tar, (iii) measuring NRR-HA of a second suitably-prepared sample of the pyrolysis tar, and (iv) comparing NRR to NRR-HA to determine NRR-LA and whether the pyrolysis tar will have a tendency to foul a hydroprocessing reactor operating under the desired hydroprocessing conditions.

[0031] Further aspects include methods for blending pyrolysis tars to achieve a desired radical profile, which is indicated when a suitably-prepared sample of the blend has an NRR value of greater than 0.5 mmol/g-oil in 10 minutes at 400°C, an NRR-HA value of greater than 0.2 mmol/g-oil in 10 minutes at 400°C, and/or an NRR-LA value of greater than 0.15 mmol/g- oil in 10 minutes at 400 °C.

[0032] The present disclosure is not limited to these aspects, and this description is not meant to foreclose other aspects within the broader scope of the invention.

Production of Pyrolysis Tar

[0033] Pyrolysis tars are a by-product of a pyrolysis process. Pyrolysis tar can be produced by exposing a hydrocarbon-containing feed to pyrolysis conditions in order to produce a pyrolysis effluent, the pyrolysis effluent being a mixture comprising unreacted feed, unsaturated hydrocarbon produced from the feed during the pyrolysis, and pyrolysis tar. For example, when a feed comprising 10 wt% hydrocarbon or greater, based on the weight of the feed, is subjected to pyrolysis, the pyrolysis effluent generally contains pyrolysis tar and 1 wt% or greater of C 2 unsaturates, based on the weight of the pyrolysis effluent. The pyrolysis tar typically comprises 90 wt% or greater of the pyrolysis effluent’s molecules having an atmospheric boiling point of 290°C or greater. Generally, the pyrolysis of a hydrocarbon feed of greater molecular weight will produce a greater amount of pyrolysis tar. Besides hydrocarbon, the feed to pyrolysis may further comprise diluent, e.g., one or more of nitrogen, water, etc. For example, the feed may further comprise 1 wt% or greater diluent based on the weight of the feed, such as 25 wt% or greater. When the diluent includes an appreciable amount of steam, the pyrolysis is referred to as steam cracking. The hydrocarbon product of a steam cracker furnace generally includes (i) lower molecular weight compounds such as one or more of acetylene, ethylene, propylene, butenes, and (ii) higher molecular weight compounds such as one or more C₅₊ compounds, and mixtures thereof, including SCT. SCT is typically separated from the aqueous and/or hydrocarbon product of a steam cracker in one or more separation stages. Other streams that may be separated from the steam cracking furnace effluent include one or more of (a) steam-cracked naphtha (“SCN”, e.g., C₅ to C10 species) and steam cracked gas oil (“SCGO”), the SCGO comprising > 90 wt% based on the weight of the SCGO of molecules (e.g., C₁₀ to C₁₇ species) having an atmospheric boiling point in the range of about 400°F to 550°F (200°C to 290°C). SCT is typically included in a separator bottoms stream, which typically comprises 90 wt% or greater SCT, based on the weight of the bottoms stream. The SCT can have, e.g., a boiling range of about 550°F (290°C) or greater and can comprise molecules and mixtures thereof having a number of carbon atoms of about 15 or greater.

[0034] Steam cracking furnaces typically include two main sections: a convection section and a radiant section, the radiant section typically containing fired heaters. Flue gas from the fired heaters is conveyed out of the radiant section to the convection section. The flue gas flows through the convection section and is then conducted away, e.g., to one or more treatments for removing combustion by-products such as NO_x. Hydrocarbon is introduced into tubular coils (convection coils) located in the convection section. Steam is also introduced into the coils, where it combines with the hydrocarbon to produce a pyrolysis feed. The combination of indirect heating by the flue gas and direct heating by the steam leads to vaporization of at least a portion of the pyrolysis feed’s hydrocarbon component. The pyrolysis feed containing the vaporized hydrocarbon component is then transferred from the convection coils to tubular radiant tubes located in the radiant section. Indirect heating of the pyrolysis feed in the radiant tubes results in cracking of at least a portion of the pyrolysis feed’s hydrocarbon component. Pyrolysis effluent is conducted out of the radiant tube, and away from the pyrolysis furnace, the pyrolysis effluent comprising products resulting from the pyrolysis of the pyrolysis feedstock and any unconverted components of the pyrolysis feed. At least one separation stage is generally located downstream of the pyrolysis furnace, the separation stage being utilized for separating from the pyrolysis effluent one or more of light olefin, SCN, SCGO, SCT, water, unreacted hydrocarbon components of the pyrolysis feedstock, etc.

[0035] The pyrolysis feedstock for steam cracking typically comprises hydrocarbon and steam. In certain aspects, the pyrolysis feedstock comprises 10 wt% or greater hydrocarbon, based on the weight of the pyrolysis feedstock, e.g., 25 wt% or greater, 50 wt% or greater, such as 65 wt% or greater. Although the pyrolysis feedstock’s hydrocarbon can comprise one or more light hydrocarbons such as methane, ethane, propane, butane etc., it can be particularly advantageous to utilize a pyrolysis feedstock comprising a significant amount of higher molecular weight hydrocarbons because the pyrolysis of these molecules generally results in more pyrolysis tar than does the pyrolysis of lower molecular weight hydrocarbons. As an example, the pyrolysis feedstock can comprise 1 wt% or greater or 25 wt% or greater based on the weight of the pyrolysis feedstock of hydrocarbons that are in the liquid phase at ambient temperature and atmospheric pressure.

[0036] The hydrocarbon component of the pyrolysis feedstock comprises 10 wt% or greater, e.g., 50 wt% or greater, such as 90 wt% or greater (based on the weight of the hydrocarbon) of one or more of naphtha, gas oil, vacuum gas oil, waxy residues, atmospheric residues, residue admixtures, or crude oil; including those comprising about 0.1 wt% or greater asphaltenes. When the hydrocarbon includes crude oil and/or one or more fractions thereof, the crude oil is optionally desalted prior to being included in the pyrolysis feedstock. An example of a crude oil fraction utilized in the pyrolysis feedstock is produced by separating atmospheric pipestill (“APS”) bottoms from a crude oil followed by vacuum pipestill (“VPS”) treatment of the APS bottoms.

[0037] Suitable crude oils include, e.g., high-sulfur virgin crude oils, such as those rich in polycyclic aromatics. For example, the pyrolysis feedstock’s hydrocarbon can include > 90 wt% of one or more crude oils and/or one or more crude oil fractions, such as those obtained from an atmospheric APS and/or VPS; waxy residues; atmospheric residues; naphthas contaminated with crude; various residue admixtures; and SCT. In these aspects, the steam cracking conditions generally include one or more of (i) a temperature in the range of 760°C to 880°C, (ii) a pressure in the range of from 1 to 5 bars (absolute), or (iii) a cracking residence time in the range of from 0.10 to 2 seconds.

Pyrolysis Effluent

[0038] A pyrolysis effluent is conducted away from the pyrolysis furnace, e.g. away from a steam cracker furnace. Pyrolysis tar such as SCT is contained in the furnace’s effluent. When utilizing the pyrolysis feedstock and pyrolysis conditions of one or more of the preceding aspects, the pyrolysis effluent generally comprises 1 wt% or greater of C2 unsaturates and 0.1 wt% or greater of TH, the weight percents being based on the weight of the pyrolysis effluent. Optionally, the pyrolysis effluent comprises 5 wt% or greater of C2 unsaturates and/or 0.5 wt% or greater of TH, such as 1 wt% or greater TH. Although the pyrolysis effluent generally contains a mixture of the desired light olefins, SCN, SCGO, pyrolysis tar (such as SCT), and unreacted components of the pyrolysis feedstock (e.g., water in the case of steam cracking, but also in some cases unreacted hydrocarbon), the relative amount of each of these generally depends on, e.g., the pyrolysis feedstock’s composition, pyrolysis furnace configuration, process conditions during the pyrolysis, etc. The pyrolysis effluent is generally conducted away from the pyrolysis section, e.g., for cooling and separation.

[0039] In certain aspects, the pyrolysis effluent’s TH comprise 10 wt% or greater of TH aggregates having an average size in the range of 10 nm to 300 nm in at least one dimension and an average number of carbon atoms of 50 or greater, the weight percent being based on the weight of Tar Heavies in the pyrolysis effluent. Generally, the aggregates comprise 50 wt% or greater, e.g., 80 wt% or greater, such as 90 wt% or greater of TH molecules having a C:H atomic ratio in the range of from 1 to 1.8, a molecular weight in the range of 250 to 5000, and a melting point in the range of l00°C to 700°C.

[0040] Although not required, the pyrolysis effluent is typically cooled downstream of the pyrolysis furnace. Generally, a cooling stage is located between the pyrolysis furnace and the separation stage. Conventional cooling means can be utilized by the cooling stage, e.g., one or more of direct quench and/or indirect heat exchange (e/g/, transfer line heat exchange), but the invention is not limited thereto. For example, the transfer-line heat exchangers can cool the pyrolysis effluent to a temperature in the range of about 700°C to 350°C, in order to efficiently generate super-high pressure steam which can be utilized by the process or conducted away. If desired, the pyrolysis effluent can be subjected to direct quench, e.g., at a location between the furnace outlet and the separation stage. Pyrolysis Tars

[0041] At least one separation stage is typically utilized downstream of the pyrolysis furnace and downstream of the transfer line exchanger and/or quench location. Generally, the separation stage removes one or more of light olefin, SCN, SCGO, pyrolysis tars (e.g. SCT), and water from the pyrolysis effluent. Conventional separation equipment can be utilized in the separation stage, e.g., one or more flash drams, fractionators, water-quench towers, indirect condensers, etc., such as those described in U.S. Patent No. 8,083,931. The separation stage can be utilized for separating a pyrolysis tar stream (or in the event of steam cracking, an SCT stream) from the pyrolysis effluent. The pyrolysis tar stream typically contains 90 wt% or greater of pyrolysis tar or SCT, based on the weight of the tar stream, e.g., 95 wt% or greater, such as 99 wt% or greater, with 90 wt% or greater of the balance of the tar stream being particulates, for example. The tar stream comprises 10% or greater (on a weight basis) of the pyrolysis effluent’s TH, based on the weight of the pyrolysis effluent’s tar heavies. The pyrolysis tar stream can be obtained, e.g., from an SCGO stream and/or a bottoms stream of the steam cracker’s primary fractionator, from flash-drum bottoms (e.g., the bottoms of one or more flash drams located downstream of the pyrolysis furnace and upstream of the primary fractionator), or a combination thereof. For example, the pyrolysis tar stream can be a mixture of primary fractionator bottoms and tar knock-out dram bottoms.

[0042] The pyrolysis tar can be an SCT, for example. SCT generally comprises 50 wt% or greater, such as, 90 wt% or greater, of the pyrolysis effluent’s TH based on the weight of the pyrolysis effluent’s TH. Another way of saying this is that the pyrolysis effluent’s tar heavies comprise a wt% SCT based on the weight of the pyrolysis effluent’s tar heavies. For example, the SCT can have (i) a TH content in the range of from 5 wt% to 40 wt%, based on the weight of the SCT, (ii) an API gravity (measured at a temperature of l5.8°C) of -7.5 API or less, such as -8 API or less, or -8.5°API or less; and (iii) a 50°C viscosity in the range of 200 cSt to 1.0 x 10⁷ cSt. The SCT can have, e.g., a sulfur content that is greater than 0.5 wt%, e.g., in the range of 0.5 wt% to 7 wt%, based on the weight of the SCT. In aspects where pyrolysis feedstock does not contain an appreciable amount of sulfur, the SCT can comprise 0.5 wt% or less sulfur, e.g., 0.1 wt% or less, such as 0.05 wt% or less sulfur, based on the weight of the SCT. The amount of olefin in the SCT is generally 10 wt% or less, e.g., 5 wt% or less, such as 2 wt% or less, based on the weight of the SCT. More particularly, the amount of (i) vinyl aromatics in the SCT is generally 5 wt% or less, e.g., 3 wt% or less, such as 2 wt% or less and/or (ii) aggregates in the SCT which incorporate vinyl aromatics is generally 5 wt% or less, e.g., 3 wt% or less, such as 2 wt% or less, the weight percents being based on the weight of the SCT. In one aspect, the pyrolysis tar has an I_N greater than 80 and greater than 70 wt% of the pyrolysis tar’s molecules have an atmospheric boiling point of greater than 290°C.

[0043] A steam cracker tar typically comprises 50 wt% or greater of the steam cracker effluent’s TH, based on the weight of the steam cracker effluent’s TH, e.g., 75 wt% or greater, such as 90 wt% or greater. The SCT can have, e.g., (i) a sulfur content in the range of 0.5 wt% to 7 wt%, based on the weight of the SCT; (ii) a TH content in the range of from 5 wt% to 40 wt%, based on the weight of the SCT; (iii) a density at l5°C in the range of 1.01 g/cm³ to 1.19 g/cm³, e.g., in the range of 1.07 g/cm³ to 1.18 g/cm³; and (iv) a 50°C viscosity in the range of 200 cSt to 1.0 x 10⁷ cSt. The amount of olefin in the SCT is generally 10 wt% or less, e.g., 5 wt% or less, such as 2 wt% or less, based on the weight of the pyrolysis tar or SCT. More particularly, the amount of (i) vinyl aromatics in the SCT and/or (ii) aggregates in the SCT which incorporate vinyl aromatics is generally 5 wt% or less, e.g., 3 wt% or less, such as 2 wt% or less, based on the weight of the SCT.

[0044] Optionally, the SCT has a density measured at l5°C in the range of 1.01 g/cm³ to

1.19 g/cm³. The invention is particularly advantageous for SCT’s having density at l5°C that is 1.10 g/cm³ or greater, e.g., 1.12 g/cm³ or greater, 1.14 g/cm³ or greater, 1.16 g/cm³ or greater, or 1.17 g/cm³ or greater. Optionally, the SCT has a viscosity measured at 50°C in the range of 200 cSt to 1.0 x 10⁷ cSt, e.g., 1.0 x 10⁴ cSt or greater, such as 1.0 x 10⁵ cSt or greater, or 1.0 x 10⁶ cSt or greater, or 1.0 x 10⁷ cSt or greater.

[0045] Optionally, the SCT has a normal boiling point of 290°C or greater, a viscosity at l5°C of 1 x 10⁴ cSt or greater, and a density of 1.1 g/cm³ or greater. The SCT can be a mixture which includes a first SCT and one or more additional pyrolysis tars, e.g., a combination of the first SCT and one or more additional SCTs. When the SCT is a mixture, it is typical for at least 70 wt% of the mixture to have a normal boiling point of at least 290°C, and include free radicals. When the mixture comprises first and second pyrolysis tars (one or more of which is optionally an SCT) 90 wt% or greater of the second pyrolysis tar optionally has a normal boiling point of 290°C or greater.

[0046] Precipitation of particulates (e.g., asphaltenes) during and after blending is lessened when the first pyrolysis tar (which may itself be a mixture of pyrolysis tars) has an SBN > 135 and an IN > 80 and the SBN of the blended tar composition is at least 20 solvency units greater than the second pyrolysis tar’s (and/or the blended pyrolysis tar’s) IN. For example, it can be desirable to carry out blending such that (i) the first pyrolysis tar has an SBN > 135 and an IN > 80, (ii) the second pyrolysis tar has an SBN that is less than that of the first pyrolysis tar, (iii) the blended tar composition has an S_BN that is less than that of the first pyrolysis tar, (iv) the second pyrolysis tar (and/or the blend) has an I_N that is less than that of the first pyrolysis tar, and (v) the S_BN of the blended tar composition is at least 20 solvency units greater than the second pyrolysis tar’s I_N, such as at least 30 solvency units, such as at least 40 solvency units greater than the second pyrolysis tar’s I_N. Optionally, the second tar’s (or any additional tar’s) I_N is less than the S_BN of the final pyrolysis tar blend.

[0047] In at least one embodiment, a tar of the present disclosure can have 0 mmol of reactive radicals NRR in 10 minutes at 250°C, such as 0.1 or greater mmol/g-oil in 10 minutes at 250°C, such as 0.2 or greater mmol/g-oil in 10 minutes at 250°C, based on the amount of DHDS measured in a process of the present disclosure, where the DHDS is the reaction product of an HDS having a bond dissociation energy of one or more C-H bonds of 330 kJ/mol or less. A tar of the present disclosure can have an NRR of 2 mmol/g-oil or greater in 10 minutes at 400°C, such as 3 or greater mmol/g-oil in 10 minutes at 400°C, such as 4 or greater mmol/g-oil in 10 minutes at 400°C, such as 5 mmol/g-oil or greater in 10 minutes at 400°C, based on the amount of DHDS measured in a process of the present disclosure, where the DHDS is the reaction product of an HDS having a bond dissociation energy of one or more C-H bonds of 330 kJ/mol or less. In at least one embodiment, if a tar has an NRR value 0.5 mmol/g-oil in 10 minutes at 400°C or less, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking).

[0048] A tar of the present disclosure can have high activity reactive radicals (NRR-HA) of 1 mmol/g-oil or greater in 10 minutes at 400°C, such as 1.5 mmol/g-oil or greater in 10 minutes at 400°C, such as 2 mmol/g-oil or greater in 10 minutes at 400°C, based on the amount of DHDS measured in a process of the present disclosure, where the DHDS is the reaction product of an HDS having a bond dissociation energy of one or more C-H bonds of greater than 330 kJ/mol. In at least one embodiment, if a tar has an NRR-HA value 0.2 mmol/g- oil in 10 minutes at 400°C or less, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking).

[0049] A tar of the present disclosure can have low activity reactive radicals (NRR-LA) of 1 or greater mmol/g-oil in 10 minutes at 400°C, such as 2 or greater mmol/g-oil in 10 minutes at 400°C, such as 3 or greater mmol/g-oil in 10 minutes at 400°C, as determined by subtracting NRR-HA in an amount of time at a temperature from NRR for the same amount of time at the same temperature used to determine NRR-HA. If a tar has an NRR-LA value 0.15 mmol/g-oil in 10 minutes at 400°C or less, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking).

[0050] When a pyrolysis tar exhibits an NRR value of greater than 0.5 mmol/g-oil in 10 minutes at 400°C, an NRR-HA value of greater than 0.2 mmol/g-oil in 10 minutes at 400°C, an NRR-LA value of greater than 0.15 mmol/g-oil in 10 minutes at 400°C, blending the pyrolysis tar with a second tar having a lesser NRR value, NRR-HA value, and/or NRR-LA value can be used to produce a pyrolysis tar blend having an NRR value of less than 0.5 mmol/g-oil in 10 minutes at 400°C, an NRR-HA value of less than 0.2 mmol/g-oil in 10 minutes at 400°C, and/or an NRR-LA value of less than 0.15 mmol/g-oil in 10 minutes at 400°C.

[0051] Should a lesser N value (NRR, NRR-HA, or NRR-LA) be desired for the desired hydroprocessing conditions, long term hydroprocessing without appreciable fouling can be achieved by blending the sampled tar with a second pyrolysis tar having an N value less than an N value that would otherwise promote reactor fouling. For example, a blend’ s desired N value can be estimated from the radical concentrations of the first and second pyrolysis tar components, (NTI and NT2) using the formula:

Nj_biend, about {(Nti * grams tar 1) + (NT2 * grams tar 2)]/(grams tar 1 + grams tar 2).

[0052] N_Tbiend can be readily determined using the methods specified for measuring an N value of an individual pyrolysis tar. In certain aspects, the elevated temperature for use in the procedure (T₂) is the temperature of the desired hydroprocessing reaction (or greater), and the residence time t_h at the elevated temperature, before quenching, is at least the expected residence time of the hydroprocessing reaction or greater.

[0053] For instance, a hydroprocessing is to take place at or above 400°C, and a residence time of 10 minutes or greater using a tar having an NTI under these conditions that is NRR-LA of 0.15 mmol/g-oil or less in 10 minutes at 400°C. A first SCT (SCT 1) is evaluated for suitability as a feed to this process by determining a low activity reactive radical content (NRR-LA) using a method of the present disclosure. If NRR-LA is 0.15 or less, no alteration or blending of the SCT is indicated before hydroprocessing. If however NRR-LA is greater than 0.15, fouling potential of the tar is lessened by blending SCT1 with a second SCT (SCT 2), where NT2 (i.e., NRR-LA of SCT 2) is less than 0.15 mmol/g-oil in 10 minutes at 400°C for SCT2. For instance, if NTI is about 0.2 and NT2 is about 0.1, then a blend of 100 grams of SCT1 with about 100 grams of SCT2 (e.g., using a blend ratio of (wt% SCT2 in blend / wt% SCT 1 in blend) aboutkl) is estimated to produce a blended SCT with an estimated N_Tbiend (i.e., NRR-LA of the blend) about 0.15 mmol/g-oil in 10 minutes at 400°C. If a blended sample measured Nibiend is still greater than 0.15, the blend ratio may be increased, for instance using (wt% SCT2 in blend/wt% SCT 1 in blend) = 60:40, and retest the new blend using a process of the present disclosure. For a further decreasing in fouling potential, blending can be continued beyond the blend ratio where Ntwbh_ά does not exceed a desired N value_, e.g., to achieve an Ni_biend of 0.9 or less of the desired N value, such as Ni_biend of 0.75 or less of the desired N value, or Nt_ΐw of 0.5 or less of the desired N value.

[0054] In other aspects, instead of (or in addition to) blending, when Ni_biend exceeds a desired N value, the measured Nmi_end can be used as an indicator of the potential fouling characteristics of the particular pyrolysis tar, and the blend can be sent away.

Pyrolysis Tar Radical Profile

[0055] The fouling tendency of a pyrolysis tar during hydroprocessing varies from one batch to another depending upon, for example, the pyrolysis tar’s thermal history during pyrolysis and thereafter. While not wishing to be bound by any particular theory, it is believed that the tendency of a pyrolysis tar to foul can be determined based on the concentrations of free radicals in a suitably-prepared sample of the pyrolysis tar. The pyrolysis tar sample’s free radical content can be determined by measuring an amount of DHDS, for example.

[0056] In at least one embodiment, a pyrolysis tar at a temperature Ti of 350°C or less is evaluated for its potential for fouling the reactor at desired hydroprocessing conditions. The evaluation is undertaken by sampling the pyrolysis tar, adding an HDS to the pyrolysis tar sample, raising the temperature of the sample to a predetermined temperature T₂ that is at least l0°C greater than Ti, for a predetermined period of time t_h. Typically, T₂ is substantially the same as the desired hydroprocessing temperature, and t_h is substantially the same as the time during which the tar is exposed to hydroprocessing conditions. Following this, the sample is cooled to a temperature T₃ < Ti, and an amount of DHDS is measured to determine an amount of reactive radicals NRR).

[0057] Without being bound by theory, during heavy oil cracking, the quantities of reactive radicals abstracting H· from different HDSs might not be the same due to the different C-H bond dissociation energy in different HDSs. If the activities of reactive radicals are sufficiently high, they would readily abstract H· from different HDSs and the differences in their quantities detected by different HDSs would be minimal. Conversely, if the activities of reactive radicals are low, the differences in quantities of reactive radicals detected by different HDSs would be large. Therefore, the quantities of H· abstracted from different HDSs can be used to measure the activity of reactive radicals as well as the bonding structure of heavy oils. Hence, HDSs having different hydrogen donor capabilities than each other enable the measurement of radical concentrations, thus varying according to the degree of reactivity.

[0058] Accordingly, in at least one embodiment, a second portion (second sample) of the pyrolysis tar (at a temperature T₄ of 350°C or less) is sampled, a second HDS (different from the first HDS) is added to the sample, the temperature of the sample is raised to temperature T5 for period of time t_h2. Following this, the sample is cooled to temperature T₆, and the amount of second DHDS is measured to determine an amount of high activity radicals (NRR- HA). In at least one embodiment, Ti = T₄, T2 = T5 and th = th2. In at least one embodiment, T3 = T₆.

[0059] The amount of low activity radicals (NRR-LA) can then be determined by subtracting the amount of NRR-HA) from NRR. If a tar has an NRR-LA value of 0.15 or less mmol/g-oil or less in 10 minutes at 400°C, then the tar can be provided to hydroprocessing without one or more additional pretreatment processes (such as thermal cracking). Alternatively, a tar having an NRR-LA value of greater than 0.15 mmol/g-oil in 10 minutes at 400°C may be blended with a second pyrolysis tar and/or utility fluid to reduce the free radical content of the blended tar for hydroprocessing.

[0060] Aspects of the present disclosure also include (i) obtaining a sample of a pyrolysis tar, (ii) measuring NRR of a suitably-prepared sample of the pyrolysis tar, (iii) measuring NRR- HA of a second suitably-prepared sample of the pyrolysis tar, and (iv) comparing NRR to NRR- HA to determine NRR-LA, which can provide whether the pyrolysis tar will have a tendency to foul a hydroprocessing reactor operating under the desired hydroprocessing conditions.

[0061] A suitable amount, e.g., 5.5 ± 1 mg, of the cooled pyrolysis tar is loaded into a glass capillary having a diameter of about 1.1 mm. An amount of HDS is also loaded into the glass capillary. In at least one embodiment, a mass ratio of tar to HDS is from 1:1 to 1:5, such as from 1:2.5 to 1:3. Alternatively, a mass ratio of tar to HDS is from 0.1:1 to 4:1, such as from 0.5:1 to 2:1, such as from 0.9:1 to 1:0.9. It has been discovered that HDS in these ratios can provide suitable determination of the amounts of HDS and DHDS in an HPLC chromatogram without interference from oil components.

[0062] The sample can occupy about 10 mm of the capillary’s length. Although the capillary can be loaded at any convenient temperature Ti or T₄ < 350°C, it can be beneficial to expose the pyrolysis tar to a temperature of l00°C for 1 hr. in an oven before introducing HDS into the capillary in order to decrease the viscosity of the tar for easier loading of the capillary. The sample loaded capillary is weighed and then placed inside a glass tube of 2 mm diameter x 30 mm length. The glass tube is purged with nitrogen for at least about 15

44 seconds and then sealed by exposing each end of the tube to a burner. Purging is believed to effectively limit the influence of oxygen on the reaction and on the free radical measurement.

[0063] The sample is prepared by exposing it to a temperature T₂ is greater than or equal to Ti + lO°C, for a heating time t_h to produce additional free radicals in the sample. Heating rate is adjusted so that the sample is substantially in thermal equilibrium at temperature T₂ within a time less than or equal to t_h, e.g., 0.75*t_h or less, such as 0.5*t_h or less, or 0.25*t_h or less, or 0.l*t_h or less. Temperature T₂ is typically 375°C or greater, e.g., 400°C or greater, or 420°C or greater, or 440°C or greater, or 460°C or greater, or 480°C or greater, or 500°C or greater. Heating time t_h is 30 seconds or greater, e.g., 1 minute or greater, such as 1.5 minutes or greater, or 2 minutes or greater, or 2.5 minutes or greater, or 3 minutes or greater, or 5 minutes or greater, or 7.5 minutes or greater, or 10 minutes or greater, or 15 minutes or greater, or 20 minutes or greater, or 30 minutes or greater, or 40 minutes or greater. In certain aspects, temperature T₂ is substantially the same as the average bed temperature of the hydroprocessing reactor, and t_h is substantially the same as the average residence time of the pyrolysis tar in the hydroprocessing reactor. Doing so has been found to increase the effectiveness of the comparison of NRR and NRR-HA, particularly when NRR is established under substantially the same conditions as NRR-HA.

[0064] Sample preparation also includes cooling (e.g., quenching) the heated sample from T₂ to a temperature T₃, wherein T₃ is less than Ti. Cooling rate is adjusted so that the sample is substantially in thermal equilibrium at temperature T₃ within a time t_h or less, e.g., 0.75*t_h or less, such as 0.5*t_h or less, or 0.25*t_h or less, or 0.l*t_h or less.

[0065] For a second sample, the sample is prepared by exposing it to a temperature T5 greater than or equal to T₄ + l0°C, for a heating time t_h2 to produce additional free radicals in the sample. Heating rate is adjusted so that the sample is substantially in thermal equilibrium at temperature T5 within a time less than or equal to th₂, e.g., 0.75*th₂ or less, such as 0.5*th₂ or less, or 0.25*t_h2 or less, or 0.l*t_h2 or less. Temperature T5 is typically 375°C or greater, e.g., 400°C or greater, or 420°C or greater, or 440°C or greater, or 460°C or greater, or 480°C or greater, or 500°C or greater. Heating time t_h2 is 30 seconds or greater, e.g., 1 minute or greater, such as 1.5 minutes or greater, or 2 minutes or greater, or 2.5 minutes or greater, or 3 minutes or greater, or 5 minutes or greater, or 7.5 minutes or greater, or 10 minutes or greater, or 15 minutes or greater, or 20 minutes or greater, or 30 minutes or greater, or 40 minutes or greater. In certain aspects, temperature T5 is substantially the same as the average bed temperature of the hydroprocessing reactor, and t_h2 is substantially the same as the average residence time of the pyrolysis tar in the hydroprocessing reactor. Doing so has been found

45 to increase the effectiveness of the comparison of NRR and NRR-HA, particularly when NRR is established under substantially the same conditions as NRR-HA.

[0066] Sample preparation also includes cooling (e.g., quenching) the heated sample from T5 to a temperature T₆, wherein T₆ is less than T₄. Cooling rate is adjusted so that the sample is substantially in thermal equilibrium at temperature T₆ within a time ti,2 or less, e.g., 0.75*t_h2 or less, such as 0.5*t_h2 or less, or 0.25*t_h2 or less, or 0.1¾₂ or less.

[0067] NRR and NRR-HA can be determined by any convenient method, including conventional methods such as HPLC. HPLC can measure an amount of DHDS indicative of the amount of H radicals in a sample. The HPLC measurements are performed at a column temperature of from 25 °C to 50°C and mobile phase at a flow rate of from 0.5 mL/min to 2 mL/min. The mobile phase can include an aliphatic solvent, such as C4-C20 alkyl, such as hexane. In at least one embodiment, measuring includes measuring the amount of DHDS by HPLC with a chromatograph including a diode array detector. The detector can be operated at any suitable wavelength for detecting DHDS. In at least one embodiment, the wavelength for detecting DHDS is from 150 nm to 400 nm, such as from 200 nm to 300 nm, such as from 200 nm to 250 nm, for example about 210 nm or about 220 nm.

[0068] Typically, the method selected for measuring NRR is substantially the same as the method utilized for measuring NRR-HA. Suitable instruments for HPLC include Waters e2695 equipped with a Waters 2998 diode array detector. The HPLC measurements can be carried out at any convenient temperature T3 or less or T₆ or less, e.g., ambient temperature.

[0069] In certain aspects, the pyrolysis tar is selected from among those where at least 70 wt% of the pyrolysis tar mixture has a normal boiling point of at least 290°C, and optionally having an IN > 80.

[0070] Alternatively, a pyrolysis tar sample’s total free radical content (of radicals stable at room temperature) can be measured using a suitable ESR process, for example, where the pyrolysis tar sample is prepared by (i) separating a suitably- sized sample from the pyrolysis tar at a temperature T₇ that is 350°C or less, (ii) exposing the sample to an elevated temperature that exceeds T₇ by at least l0°C for a heating time t_h3, (iii) cooling the sample to a temperature of T₇ or less, and (iv) determining the free radical content of the cooled sample, e.g., using ESR. The ESR measurement can be carried out at a temperature of T₇ or less, e.g., at ambient temperature. Total free radical content (RT) can be determined from cooled pyrolysis tar samples by ESR. The ESR measurement can be carried out at a temperature of T₇ or less, e.g., at ambient temperature. RT can be determined from cooled pyrolysis tar samples by ESR. Hydrogen Donor Solvents

[0071] An HDS is a solvent capable of reacting with a free radical by donating a hydrogen atom (e.g., to the free radical moiety) to form a DHDS, also referred to as a DHDS.

[0072] In at least one aspect, the“second HDS” is an HDS capable of reacting with high activity radicals and is independently represented by formula (I):

(I).

Each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, and R¹⁰ is independently hydrogen or C1-C20 alkyl. C1-C20 alkyl can be substituted or unsubstituted. Each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, and R¹⁰ can be hydrogen. In at least one embodiment, a mass ratio of tar to HDS is from 0.1:1 to 4: 1, such as from 0.5: 1 to 2:1, such as from 0.9:1 to 1:0.9. In at least one embodiment, a DHDS is a naphthalene. A first HDS can be l,2,3,4-tetrahydronaphthalene.

[0073] In at least one embodiment, an HDS capable of reacting with high activity and low activity radicals, the“first HDS” is independently represented by formula (II):

Each of R¹ , R² , R³ , R⁴ , R⁵ , R⁶ , R⁷ , R⁸ , R⁹ , and R¹⁰ is independently hydrogen or C1-C20 alkyl. In at least one embodiment, each of R¹ , R² , R³ , R⁴ , R⁵ , R⁶ , R⁷ , R⁸ , R⁹ , and R¹⁰ is hydrogen. In at least one embodiment, a mass ratio of tar to HDS is from 1:1 to 1:5, such as from 1:2.5 to 1:3. In at least one embodiment, the DHDS is anthracene.

[0074] In at least one embodiment, an HDS is selected from 9,l0-dihydroanthracene, l,2,5,6-tetrahydroanthracene, l,4,9,l0-tetrahydroanthracene, l,2-dihydronaphthalene, 3,4- dihydronaphthalene, l,2,3,4-tetrahydronaphthalene, l,2,3,4-tetrahydrophenanthrene, 1,4- dihydrobenzene and cyclohexane.

[0075] As discussed above, an HDS of a first sample is different (e.g., has a different chemical structure) than an HDS of a second sample. For example, an HDS of a first sample is an HDS represented by formula (I), whereas an HDS of a second sample is an HDS represented by formula (II). Alternatively, an HDS of a first sample is an HDS represented by formula (II), whereas an HDS of a second sample is an HDS represented by formula (I).

[0076] HDSs having different chemical structures can differ in C-H bond dissociation energies. In at least one embodiment, an HDS of a first sample and/or second sample independently has a bond dissociation energy of 330 kJ/mol or lower, such as from 100 kJ/mol to 330 kJ/mol, such as from 200 kJ/mol to 330 kJ/mol, such as from 300 kJ/mol to 330 kJ/mol, such as from 300 kJ/mol to 328 kJ/mol, such as from 320 kJ/mol to 327 kJ/mol. HDSs having a C-H bond dissociation energy of 330 kJ/mol or lower can provide determination of reactive radicals (NRR) in a heavy oil sample. In at least one embodiment, an HDS represented by formula (II) has a bond dissociation energy of 330 kJ/mol or lower. Alternatively, an HDS of a first sample and/or second sample independently has a bond dissociation energy of greater than 330 kJ/mol, such as from 331 kJ/mol to 500 kJ/mol, such as from 335 kJ/mol to 400 kJ/mol, such as from 340 kJ/mol to 400 kJ/mol, such as from 340 kJ/mol to 350 kJ/mol. HDSs having a C-H bond dissociation energy of greater than 330 kJ/mol can provide determination of high reactivity reactive radicals (NRR-HA) in a heavy oil sample. In at least one embodiment, an HDS represented by formula (I) has a bond dissociation energy of greater than 330 kJ/mol.

Tar Process Overview

[0077] NRR, NRR-HA, and NRR-LA values of the present disclosure can be used to determine desired treatment (e.g., pretreatment) processes. For example, the values can be used to determine steam cracking process conditions, such as temperature and residence time, and can be used to determine if tar processing procedures, such as thermal treatment, centrifugation, or guard reactor processes, can be bypassed completely. Fig. 1 is a process flow diagram illustrating an overview of certain aspects of a process of the present disclosure. A tar stream to be processed A is thermally treated (e.g., steam cracked) to reduce reactivity during transport to a centrifuge B. The above described N values (NRR, NRR-HA, and NRR-LA) can be used to determine desired pretreatment conditions. A utility fluid J (which may act as a solvent for at least a portion of the tar’ s hydrocarbon compounds) may be added to the tar stream to reduce viscosity. Utility fluid may be recovered from the process for recycle (e.g., as shown in FIG. 1). A filter (not shown) may be included in the transport line to remove relatively large insoluble material, e.g., relatively large solids. The thermally processed tar stream is centrifuged to remove insoluble material (e.g., solids) larger than 25 pm. The “cleared” liquid product tar stream is fed to a guard reactor D (which can include a plurality of guard reactors (not shown), e.g., an online guard reactor and an offline guard reactor), via a pretreatment manifold C, which directs the tar stream in an online guard reactor and/or a guard reactor that can be held offline, for instance for maintenance. The above described N values (NRR, NRR-HA, and NRR-LA) can also be used to determine desired pretreatment guard reactor conditions. The guard reactor is typically operated under mild hydroprocessing conditions to further reduce the tar reactivity. The effluent from the guard reactor passes through an outlet manifold E to a pretreatment hydroprocessing reactor F for further hydroprocessing under somewhat harsher conditions and with a more active catalyst. The above described N values (NRR, NRR-HA, and NRR-LA) can be used to determine desired pretreatment hydroprocessing conditions. The effluent from the pretreatment hydroprocessing reactor passes to a main hydroprocessing reactor G for further hydroprocessing under yet more severe conditions to obtain a Total Liquid Product (“TLP”) that is of blending quality, but typically remains somewhat high in sulfur. Recovery facility H includes at least one separation, e.g., fractionation, for separating from the TLP (i) a light stream K suitable for fuels use, (ii) a bottom fraction I which includes heavier components of the TLP, and (iii) a mid-cut. At least a portion of the mid-cut can be recycled to the tar feed as utility fluid via line J. The bottoms fraction I can be fed to a 2^nd Stage hydroprocessing reactor (not shown) for an additional hydroprocessing that provides desulfurization. The effluent stream from the 2^nd Stage hydroprocessing reactor is of low sulfur content and is suitable for blending into an ECA (“Emission Control Area”) or LSFO (“Low Sulfur Fuel Oil”) compliant fuel.

Experimental Results

Characterization of Heavy Oils

[0078] Heavy oils were provided by ExxonMobil Chemical Company. The heavy oils are black liquid of poor fluidity at room temperature. Their elemental composition was determined by analysis using an elemental analyzer (Vario EL cube). Their SARA composition (Saturates, Aromatics, Resins and Asphaltenes) was determined according to the Chinese national standards NBSHT 0509-2010, in which the asphaltenes was precipitated out by n-heptane and the n-heptane soluble fractions were quantified by chromatograph separation with an alumina column.

[0079] The average molecular structure of the oils was determined with a cross polarization magic angle spinning (CP/MAS) ¹³C nuclear magnetic resonance spectrometer (¹³C NMR, Bruker AV-300) at a resonance frequency of 75.47 MHz at room temperature with the contact time of 1 ms, a MAS rotation speed of 12.0 kHz, and the recycle delay time of 0.5- 1.5 s. FIG. 2 is ¹³C NMR spectra of the oils, according to one embodiment. Cracking

[0080] The heavy oils were heated to H0°C and sampled 5.5+1 mg with glass capillaries of 1.1 mm in diameter. The heavy oil sample, with or without a HDS, was placed into a glass tube of 2 mm in diameter and 30 mm in length. When an HDS, DHA (98% purity) or THN (99.5% purity) was used, the mass ratios of the heavy oil to DHA or THN were 1:2.73 and 1:1, respectively. At these ratios, the theoretical amounts of H· donated by these HDSs are the same. The cracking experiments were carried out by placing the sample-loaded glass tube into a furnace with 20 sample slots and preheated to 250°C, 300°C, 350°C or 400°C. After 1.0 min, 2.0 mins, 3.0 mins, 5.0 mins, or 10.0 mins, the glass tubes were removed from the furnace and cooled to room temperature.

Quantification of Stable Radicals

[0081] The stable radicals present in the samples before and after cracking experiments were measured by electron spin resonance (ESR) (Bruker JES-FA200) at room temperature. The ESR was operated at 9.5 GHz and 1.578 mW with a central magnitude field of 3485 G, a modulation amplitude of 1.0 G, a sweep width of 100 G, sweep time of 20.97 s, and a time constant of 0.04 s. The radical concentration was calibrated by DPPH (l,l-Diphenyl-2- picrylhydrazyl, purity over 98%).

[0082] The stable radical concentration (ASR, mol/g) is determined by Eq. (1), where MSR is the amount of radicals (mol) in the sample and m is the mass (g) of the heavy oil.

Ea. (l)

[0083] The capillary and glass tube showed little influence on the samples’ ESR results. DHA or THN alone under the cracking experiment conditions showed no radical signals. Repeated experiments showed experimental errors of less than 5%.

Quantification of Reactive Radicals

[0084] Without being bound by theory, during the thermal cracking experiment, DHA may convert to anthracene (ANT) through four possible routes: donating two H· to heavy oil generated radicals as shown in Re. (1); dehydrogenation to form hydrogen molecule (¾) as shown in Re. (2); hydrogen transfer from DHA to the aromatic rings in oils; and hydrogen transfer from DHA for hydrodesulfurization of oils to form fTS.

[0085] The amount of ¾S produced during the thermal cracking experiments were quantified by a GC-FPD and the results indicated that the maximum value was 2.27xl0⁵ g/g- oil. Therefore, the fourth route can be ignored. To verify whether the third route occurs, reaction of DHA and pyrene, a model compound of oils, was performed under the same conditions as the cracking experiment, and the products were analyzed by GC-MS. The result indicated no hydrogenated product of pyrene, confirming no hydrogen transfer from DHA to the aromatic rings. Therefore, the amount of H· donated by DHA to the heavy oil radicals (termed as AH-DHA) can be determined by Eq. (2), where AANT and Am are the amounts of ANT and H₂ generated during the cracking experiment, respectively.

Re. (1)

Re. (2)

NH-DHA - 2 x (¾r - ¾)/^moii

Eq. (2)

[0086] Similarly, hydrogen transfer from THN to the aromatic rings and S-containing groups in oils was also not observed. THN converts to naphthalene (NAP) through H· donation as shown in Re. (3) and self-dehydrogenation as shown in Re. (4). Therefore, the amount of H· donated by THN (termed as AH-THN) can be determined by Eq. (3), where ANAP and Am are the amounts of naphthalene and H₂ generated in the cracking, respectively.

Eq. (3)

[0087] The amounts of DHA and ANT in the samples were quantified by high- performance liquid chromatography (HPLC) with external standard method. The samples were dissolved in 0.5 ml CS₂ and then diluted 300 times with n-hexane before being injected into HPLC. The HPLC was Waters e2695 equipped with a Waters 2998 diode array detector operated at a wavelength of 240 nm for DHA, 220 nm for ANT and 210 nm for NAP. The column was a Waters Spherisorb NH₂ column (4.6 mmx250 mm/5 pm), the column temperature is 35°C, and the mobile phase is n-hexane (99.9%) at a flow rate of 1.0 mL/min. FIG. 3 is HPLC chromatograms of the cracking product of Oil-l at 350°C for 5 min in the presence of DHA or THN. DHA and ANT, as well as THN and NAP, can been efficiently separated by this method with little interference of baseline, which confirms reliability of this method.

[0088] Assuming the cracking of heavy oils has little influence on the dehydrogenation of HDSs (Re. (2) and Re. (4)), the amounts of H₂ generated from HDSs in the presence of the heavy oils can be estimated from their self-cracking experiments in the absence of the heavy oils. The ¾ generated by self-cracking of DHA and THN were quantified based on the amounts of the produced ANT and NAP, respectively.

[0089] Quantities of reactive radicals capped by DHA (termed as ARR-DHA) and THN (termed as ARR-THN) are equal to the quantities of H· donated by DHA and THN, respectively. The reactive radicals generated from the heavy oils in cracking can be quantified through Eq. (4) and Eq. (5).

”RR-DHA -”H-DHA Eq. (4)

½-THN ^“ ^H-THN Eq. (5)

Quantifying Tar Reactivity by Measuring Radicals using DHA - a Measure of Total Radicals

[0090] Table 1 illustrates reactive radicals versus heating time of tars, according to one embodiment. The data show the quantity of reactive radicals (NRR) determined by DHA during the heavy oils cracking under various conditions. ARR increases exponentially over time and with a higher rate at a higher temperature, agreeing with the trend generally observed in cracking of many organic matters. Oil-l was stable at 250°C with only a few reactive radicals being observed in 10 min. The reactive radicals generated from Oil-l in 10 min were 0.18 mmol/g-oil, 1.69 mmol/g-oil, 2.62 mmol/g-oil and 4.73 mmol/g-oil at 250°C, 300°C, 350°C and 400°C, respectively. Oil-2 was less reactive in comparison to Oil-l, and no reactive radicals were generated at 250°C; less reactive radicals were generated at 300°C, 350°C and 400°C, with 0.81 mmol/g-oil, 1.27 mmol/g-oil, and 3.88 mmol/g-Oil in 10 min, respectively. These data indicate that more bonds are cleaved in Oil- 1 than that in Oil-2 under the conditions used.

Table 1

[0091] The reactive radical data indicate that more bonds are cleaved in Oil-l than that in Oil-2 under the conditions used. This may be attributed to the more asphaltenes and resins in Oil-l than in Oil-2. It is recognized that asphaltenes and resins are more prone to coking, which means that these two fractions are more reactive in cracking and condensation than the other two fractions, i.e., the saturates and aromatics. From the viewpoint of molecular structure, it is commonly considered that the bonds between a- and b-carbon in C_ar-C_ai-C_ai and those between aliphatic carbon and heteroatoms, such as C_ai-0 and C_ai-S, are easily cleaved. The average side/bridge chain lengths of Oil-l and Oil-2 are similar but Oil-l contains more side/bridge chains linked to aromatic rings than Oil-2, which means more weak covalent bonds (C_ar-C_ai-C_ai) in Oil-l and may account for more bond cleavage of Oil-l in thermal cracking. The above discussion suggests that the asphaltenes and resins contain more weak covalent bonds than the saturates and aromatics.

[0092] Since cleavage of one covalent bond yields two radicals, the amount of bonds cleaved in thermal cracking (termed as A_BC) is a half of the N_RR. Therefore, the quantities of bonds cleaved in Oil-l and Oil-2 in 10 min at 300°C-400°C were 0.84-2.37 mmol/g-oil and 0.40-1.94 mmol/g-oil, respectively. The extent of bond cleavage in these oils was also evidenced by comparing their quantities with the total amounts of covalent bonds. The amounts of covalent bonds ( A_BT ) in these oils were estimated by Eq. (6). They are 153.17 mmol/g and 151.60 mmol/g for Oil-l and Oil-2, respectively. The cleavable bonds in Oil-l and Oil-2, i.e. the bonds between the a and b carbons in C_ar-C_ai-C_ai, were no more than 1.55% and 1.27% of their total bonds, respectively.

Quantity of Reactive Radicals Determined by THN

[0093] The activity of reactive radicals can be ranked by comparing the quantities of H· abstracted from different donor solvents. The bond dissociation energy of C-H bonds that can donate H· in DHA and THN are approximately 326.4 kJ/mol and 346.9 kJ/mol, respectively. Table 2 illustrates reactive radicals versus heating time of Oil-l at 400°C, and Table 3 illustrates reactive radicals versus heating time of Oil-2 at 400°C. Assuming all the reactive radicals (termed as N_RR-totai or N_RR) can abstract H· from DHA while only the highly active radicals (termed as A_RR-HA) can abstract H· from THN, the difference in quantity between N_RR-totai and A_RR-HA can be defined as the quantities of low activity radicals (termed as A_RR- LA). According to this assumption, RR-_totai equals ARR. With this ranking, the data show that both heavy oils generated low and high activity radicals at the conditions used. The reactive radicals generated in the early stage, less than 3 min for Oil-l and less than 2 min for Oil-2, were mainly of lower activity while those generated in the later stage were mainly of higher activity. For Oil-l, ARR-LA started from 1.24 mmol/g-oil at 1 min and increased to 2.18 mmol/g-oil in 10 min while ARR-HA increased from none at 1 min to 2.55 mmol/g-oil in 10 min. Similar trends were observed for Oil-2 where ARR-LA started from 0.45 mmol/g-oil at 1 min and increased to 1.47 mmol/g-oil in 10 min while ARR-HA increased from none at 1 min to 2.41 mmol/g-oil in 10 min. Oil-l generates relatively more low activity radicals than Oil-2, suggesting that Oil-l contains more weak covalent bonds than Oil-2.

Table 2

Table 3

[0094] Using this methodology, some steam cracked tar samples will show much less radicals either by DHA or THN measurement while some tar samples will show much higher levels. By comparing the amount of more reactive and total radical contents of various tar samples, one can determine the proper hydroprocessing conditions and/or whether pretreatment processes are necessary/desired. For example, for samples with a low concentration of radicals, there is no need to conduct additional heat soaking, thus saving time and expenses. Behavior of Stable Radicals

[0095] A few radicals present in tar are not accessible by other radicals due mainly to steric hindrance and therefore survived and measurable by ESR.

[0096] FIG. 4 shows the quantity of these stable radicals (termed as NSR) generated from self-cracking of the two heavy oils (i.e. in the absence of a HDS). Additionally, Oil-l and Oil-2 themselves contain stable radicals with concentrations of 0.42 pmol/g-oil and 0.62 pmol/g-oil, respectively, and the data in FIG. 4 excludes the values of heavy oils themselves. FIG. 4 shows that the NSR value is low at 250°C, detectible but fluctuates over time at 300°C, and significantly increases over time at 350°C and 400°C. Since the quantity of the stable radicals was found correlating well with coke formation, these NSR data indicate that the two heavy oils may start coking at temperatures higher than 300°C. The NSR of Oil-l was higher than that of Oil-2, which, along with the higher NRR of Oil-l than Oil-2 discussed above, suggests a possible relation between the quantity of reactive radicals and the extent of radicals’ condensation to form coke. The magnitude of NSR, several pmol/g-oil, was about one order less than that of pyrolysis-derived coal tar and bio-tar, indicating that the coking rate of the heavy oils is much less than those of coal and biomass tars.

[0097] ESR data indicate that NSR for a given temperature, increases over time, indicating additional free radicals form in the pyrolysis tar at elevated (but substantially constant temperature). This behavior is surprising, particularly since the ESR measurement is carried out after sample quenching, indicating that the additional free radicals remain in the sample even at ambient temperature. While not wishing to be bound by any particular theory, it is believed that the free radicals remain in these samples because they are confined in a structure, such as a network of hydrocarbon molecules, and that these structures allow little access to other free radicals for reacting. This NSR stability indicates that the NSR measurements taken with the above procedure (sample, elevate temp for specified time, quench, measure ESR) can be used to predict at ambient temperature the tendency for a pyrolysis tar to foul a hydroprocessing reactor during pyrolysis tar hydroprocessing.

[0098] Furthermore, changes in radical formation during thermal reactions may be modeled with zero-order kinetics. The temperature effect can be represented by the Arrhenius relation, ln k = Ao - E_a/RT, where k is rate constant, Ao is a pre-exponential factor, E_a is activation energy in J/mol, T is temperature in Kelvin (K) and R is the gas constant (8.314 J/(mol- K)). Such zero-order kinetic behavior is known to be representative of coke formation, supporting the use of R_T as a measurement of fouling potential. Relation Between Reactive Radicals and Stable Radicals in Cracking

[0099] In pyrolysis of an oil shale, ARR shows a good linear relation with ASR formed in the absence of DHA, and ARR is about 3 orders of magnitude higher than ASR. TO understand the relation between stable radicals and active radicals of different activity, NSR was correlated with NRR-LA, NRR-HA and N_RR-totai· Data values of NSR VS. NRR-LA were scattered. FIG. 5 A is a graph illustrating stable radicals versus reactive radicals of Oil-l, according to an embodiment. FIG. 5B is a graph illustrating stable radicals versus reactive radicals of Oil-2, according to an embodiment. FIGS. 5A-5B show the correlation of NSR with NRR-HA and NRR- _totai · It can be seen that the NSR increases with increasing NRR-HA and N_RR-m_ai for both oils. The close-to-origin intercepts of NRR-HA and the slightly higher slopes of NRR-HA than that of NRR- _totai for both oils indicate that the highly reactive radicals are mainly responsible for the formation of stable radicals and the role of low activity radicals in the stable radical formation is quite minor. The slopes of the fitting lines in FIGS. 5A and 5B show that about 2057 highly reactive radicals in Oil-l or 3791 highly reactive radicals in Oil-2, respectively, result in the formation of one stable radical, suggesting that Oil-l is easier to form coke than Oil-2. This is consistent with the fact that Oil-l contains more asphaltenes and resins than Oil-2 and its structural units have a higher substitutive degree of aromatic rings (S) than Oil- 2.

[00100] The structure of two heavy oils and behaviors of reactive and stable radicals generated in thermal cracking were studied. These heavy oils cracked at 300°C. The concentrations of reactive radicals generated in Oil-l were greater than the concentration of reactive radicals generated in Oil-2. For instance, in 10 min at 300°C, 350°C and 400°C concentrations of reactive radicals were 1.69 mmol/g-oil, 2.62 mmol/g-oil and 4.73 mmol/g- oil for Oil-l, respectively, while 0.81 mmol/g-oil, 1.27 mmol/g-oil and 3.88 mmol/g-oil for Oil-2, respectively. The apparent activation energies (E_L) of bond cleavage were 31.0 kJ/mol and 38.8 kJ/mol for Oil-l and Oil-2, respectively. These results combined with the composition and molecular structure of the two oils, demonstrate that more asphaltenes and a higher substitutive degree result in more bond cleavage.

[00101] Reactive radicals of low activity generate first while those of high activity generate latter, but the quantities of the latter were generally more than those of the former. The stable radicals are 3 orders of magnitude less than the reactive radicals and correlate linearly with the highly reactive radicals in quantity.

[00102] Overall, the present disclosure demonstrates methods for measuring tar reactivity comprising contacting a tar with an HDS to produce a tar-solvent mixture and measuring an amount of DHDS. Furthermore, the present disclosure provides methods that provide quantification of reactivity of tar by using HDS to capture reactive free radicals formed at high temperatures. With the use of HDS with varying hydrogen donor capabilities, radical concentrations with varying degree of reactivity can be measured/determined.

[00103] All patents, test procedures, and other documents cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent and for all jurisdictions in which such incorporation is permitted.

[00104] While the illustrative forms disclosed herein have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the example and descriptions set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty which reside herein, including all features which would be treated as equivalents thereof by those skilled in the art to which this disclosure pertains.

[00105] When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

1. A hydrocarbon process, comprising:

isolating a first sample from a heavy oil having a temperature Ti of 350°C or less; introducing a first or second hydrogen donor solvent to the sample;

exposing the first sample to a predetermined second temperature T₂ for a predetermined time t_h, wherein T₂ is greater than or equal to Ti + l0°C;

cooling the first sample to a temperature T₃, T₃ being less than or equal to Ti; and measuring an amount of dehydrogenated hydrogen donor solvent in the first sample.

2. The process of claim 1, wherein a mass ratio of heavy oil to hydrogen donor solvent is from 0.1:1 to 4: 1.

3. The process of claims 1 or 2, further comprising:

isolating a second sample from the heavy oil, wherein the heavy oil has a temperature T₄ of 350°C or less;

introducing a first or second hydrogen donor solvent to the second sample, wherein the hydrogen donor solvent is different from the hydrogen donor solvent added to the first sample;

exposing the second sample to a predetermined temperature T5 for a predetermined time t_h2, wherein T5 is greater than or equal to T₄ + l0°C;

cooling the sample to a temperature T₆, T₆ being less than or equal to T₄; and measuring an amount of second dehydrogenated hydrogen donor solvent in the sample.

4. The process of claim 3, wherein Ti = T₄; T₂ = T5; t_h = t_h2; and T₃ = Te.

5. The process of claims 3 or 4, wherein a mass ratio of heavy oil to second hydrogen donor solvent is from 0.1:1 to 4:1.

6. The process of any one of claims 2-5, further comprising comparing the amount of the first dehydrogenated hydrogen donor solvent with the amount of the second dehydrogenated hydrogen donor solvent to determine an amount of low activity radicals in the heavy oil.

7. The process of claim 6, wherein comparing comprises subtracting the amount of the first dehydrogenated hydrogen donor solvent from the amount of the second dehydrogenated hydrogen donor solvent.

8. The process of any of the preceding claims, wherein the heavy oil is derived from hydrocarbon pyrolysis.

9. The process of any of the preceding claims, wherein the heavy oil is a pyrolysis tar.

10. The process of any of the preceding claims, wherein the pyrolysis tar is a hydrocarbon-containing mixture which includes free radicals, wherein at least 70 wt% of the mixture has a normal boiling point of at least 290°C.

11. The process of any of the preceding claims, wherein the heavy oil has an NRR value of greater than 0.5 mmol/g-oil in 10 minutes at 400°C.

12. The process of any of the preceding claims, wherein the heavy oil has an NRR-HA value of greater than 0.2 mmol/g-oil in 10 minutes at 400°C.

13. The process of any of the preceding claims, wherein the first hydrogen donor solvent is represented by formula (I):

(I),

wherein each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, and R¹⁰ is independently hydrogen or C1-C20 alkyl.

14 The process of claim 13, wherein the first hydrogen donor solvent is 1, 2,3,4- tetrahydronaphthalene and the first dehydrogenated hydrogen donor solvent is naphthalene.

15. The process of any one of claims 3-14, wherein the second hydrogen donor solvent is represented by formula (II):

wherein:

each of R¹ , R² , R³ , R⁴ , R⁵ , R⁶ , R⁷ , R⁸ , R^9’, and R¹⁰ is independently hydrogen or

C1-C20 alkyl.

16. The process of claim 15, wherein each of R¹ , R² , R³ , R⁴ , R⁵ , R⁶ , R⁷ , R⁸ , R^9’, and R¹⁰ is hydrogen and the second dehydrogenated hydrogen donor solvent is anthracene.

17. A hydrocarbon conversion process using at least first and second pyrolysis tars, each pyrolysis tar being a hydrocarbon-containing mixture derived from hydrocarbon pyrolysis, wherein at least 70 wt% of the mixture has a normal boiling point of at least

290°C and the mixture includes free radicals, the process comprising:

(a) providing a pyrolysis tar composition at a temperature Ti that is less than or equal to 350°C, the pyrolysis tar composition having an initial blend ratio (wt% second pyrolysis tar in blend) : (wt% first pyrolysis tar in blend) equal to zero;

(b) isolating a sample from the pyrolysis tar composition;

(c) introducing a hydrogen donor solvent to the sample;

(d) exposing the sample to a predetermined second temperature T₂ for a predetermined time t_h, wherein T₂ is greater than or equal to Ti + l0°C;

(e) cooling the sample to a temperature T3, T3 being less than or equal to Ti, the cooled sample having a reactive radical content NRR, a high activity reactive radical content NRR-HA; and/or a low activity reactive radical content NRR-LA;

(f) and in the following conditions:

(i) when NRR does not exceed a predetermined reference reactive radical content, NRR-HA does not exceed a predetermined reference high activity reactive radical content, and/or NRR-LA does not exceed a predetermined reference low activity reactive radical content, conducting the pyrolysis tar composition to step (g), or

(ii) when NRR exceeds a predetermined reference reactive radical content, NRR-HA exceeds a predetermined reference high activity reactive radical content, and/or NRR-LA exceeds a predetermined reference low activity reactive radical content,

(A) increasing the blend ratio of the pyrolysis tar composition and repeating steps (a), (b), (c), (d), and (e) until at least achieving a second blend ratio wherein NRR of the blend does not exceed a predetermined reference reactive radical content, NRR-HA of the blend does not exceed a predetermined reference high activity reactive radical content, and/or NRR-HA of the blend does not exceed a predetermined reference low activity reactive radical content, and

(B) conducting the pyrolysis tar composition to step (g); and

(g) hydroprocessing at least a portion of the pyrolysis tar composition of step (f)(i) and/or step (f)(ii) to produce a hydroprocessed pyrolysis tar.

18. The process of claim 17, wherein 90 wt% or greater of the second pyrolysis tar has a normal boiling point of 290°C or greater, the second pyrolysis tar having a viscosity at l5°C greater than or equal to 1 x 10⁴ cSt and a density > 1.1 g/cm³.

19. The process of claims 17 or 18, wherein (i) the first pyrolysis tar has an SBN of 135 or greater and an IN of 80 or greater, and (ii) the pyrolysis tar composition has an SBN that is at least 20 solvency units greater than the IN of the pyrolysis tar composition.

20. The process of any one of claims 17-19, wherein the sample has an NRR-LA that exceeds a predetermined reference low activity reactive radical content.

21. The process of claim 20, wherein the predetermined reference low activity reactive radical content is 0.15 or greater mmol/g-oil in 10 minutes at 400°C.

22. The process of claim 21, wherein the predetermined reference low activity reactive radical content is 1 or greater mmol/g-oil in 10 minutes at 400°C.

23. A method for producing a hydroprocessed steam cracker tar, the process comprising:

(a) providing a first steam cracker tar having a temperature Ti of 350°C or less, the steam cracker tar having a density at l5°C of 1.10 g/cm³ or greater, wherein at least 70 wt% of the steam cracker tar has a normal boiling point of at least 290°C;

(b) isolating a sample from the steam cracker tar;

(c) introducing a hydrogen donor solvent to the sample and producing additional free radicals in the sample by exposing the sample to a predetermined second temperature T₂ for a predetermined time t_h, wherein T₂ is greater than or equal to Ti +lO°C;

(d) cooling the sample to a temperature T₃, T3 being less than or equal to Ti;

(e) (i) when NRR-LA does not exceed a predetermined reference low activity reactive radical content, conducting the first steam cracker tar to step (f),

(ii) when NRR-LA exceeds a predetermined reference low activity reactive radical content,

(A) providing a second pyrolysis tar at a temperature less than or equal to Ti, the second pyrolysis tar, wherein (I) the second pyrolysis tar has fewer low activity reactive radicals than the steam cracker tar, (II) is a hydrocarbon- containing mixture derived from hydrocarbon pyrolysis, and (III) at least 70 wt% of the mixture has a normal boiling point of at least 290°C; and further comprising combining the steam cracker tar with a predetermined amount of the second pyrolysis tar to produce a pyrolysis tar composition,

(B) (I) isolating a sample from the pyrolysis tar composition, (II) introducing a hydrogen donor solvent to the sample of pyrolysis tar composition, (III) exposing the pyrolysis tar composition sample to a temperature of at least T₂ for time of at least t_h, and (IV) cooling the pyrolysis tar composition sample to a temperature < T₃, the cooled pyrolysis tar composition sample having a low activity reactive radical content NRR-LA, and

(C) when NRR-LA does not exceed the predetermined reference low activity reactive radical content, either (I) conducting the pyrolysis tar composition to step (f) or (II) further increasing the amount of second pyrolysis tar in the pyrolysis tar composition and then repeating steps (e)(ii)(B) and (C); and when NRR-LA exceeds a predetermined reference low activity reactive radical content, increasing the amount of the second pyrolysis tar in the pyrolysis tar composition and then repeating steps (e)(ii)(B) and (C),

(f) producing a feed by combining with a utility fluid at least a portion of the steam cracker tar of step (e)(i) and/or at least a portion of the pyrolysis tar composition of step (e)(ii); and

(g) hydroprocessing the feed in at least one hydroprocessing zone under hydroprocessing conditions.

24. The process of claim 23, wherein the predetermined reference low activity reactive radical content (NRR-LA) is 0.15 mmol/g-oil in 10 minutes at 400°C.

25. The process of claim 24, wherein the predetermined reference NRR-LA is 1 mmol/g-oil in 10 minutes at 400°C.