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This paper is in honor of Michael (Mike) T. Klein, and his contributions to the modeling of thermal conversion are highlighted within the context of this study. The question that was posed is wheth...

Thermal conversion of bitumen by visbreaking is an important technology for partial upgrading of bitumen to pipeline transportable oil. The product from visbreaking of bitumen will likely spend a l...

The formation of new heavier material during thermal processing has long been known, and under typical visbreaking conditions, vacuum conversion of deasphalted oil is described using a first-order ...

The description of the stability index of the residue marine fuels, whose technology of production is based on the compounding visbreaking residue, light cycle gas oil, and ultralow sulfur diesel b...

The visbreaking of heavy oil in supercritical benzene (SCbenzene) was investigated. By introducing SCbenzene, the visbreaking originally occurring in the oil phase is transferred into SCbenzene. The superior diffusivity in SCbenzene improves the efficiencies of the initiation and propagation of visbreaking network, by which the reaction could be run in the desired tandem structure. By mitigating diffusion limitation to reaction kinetics, the cracking of alkyl substitutes of aromatics vital to viscosity reduction is accelerated. Being the secondary reaction of the cracking, condensation could be terminated promptly at the shortened reaction time necessary for visbreaking. A comparison between the visbreaking in SCbenzene and supercritical water (SCH2O) confirms the effectiveness of improving diffusion for the optimization on heavy oil visbreaking. Nevertheless, the optimal operating conditions involved must be determined experimentally because of the complicated interaction between phase structure and reac...

The time-dependent thermal conversion of vacuum residue deasphalted oil was studied at 280, 320, 360, and 400 °C. The vacuum residue deasphalted oil was an industrial product produced by vacuum distillation of Athabasca bitumen followed by solvent deasphalting using n-pentane. This type of visbreaking process was of interest for partial upgrading of bitumen to facilitate pipeline transport. Practically useful cracking conversion and viscosity reduction for upgrading were found only at 360 and 400 °C. The viscosity measured at 40 °C could be reduced by 3 orders of magnitude from 3720 Pa s in the feed to 2–5 Pa s in the product. The density of the product was not reduced by much, despite vacuum residue cracking conversions of 34% at 360 °C and 45–47% at 400 °C before the onset of coking. The liquid yield was 88–89%. A heavier product fraction was formed during thermal conversion. The heavy material was not necessarily asphaltenes, but an increase in n-pentane-insoluble material was also found that appeared ...

Bitumen extracted from Canada’s oil sands resources is an abundant, unconventional crude oil used to produce liquid fuels. To permit its transportation by transmission pipelines from production sites to upgraders and refineries, the highly-viscous bitumen must first be blended with up to 50 vol% of light oil (“diluent”) to produce a diluted bitumen (DB) with sufficiently low viscosity and density. Diluents occupy substantial pipeline capacity, and are relatively expensive, so Canada is developing “partial upgrading” processes to reduce the diluent content of pipeline-transportable bitumen products. Such processes lower bitumen’s density and viscosity by removing some portion of its heaviest, asphaltene-rich fraction by, for instance, solvent-induced separation and/or thermochemical conversion. Thus, processed bitumen products (PBPs) require less diluent to meet specifications for transmission pipeline transportation. We compare the minimum diluent content requirements of several PBPs meeting such specifications for density (≤ 940 kg/m3 at 15.0 °C) and viscosity (≤ 350 cSt at a pipeline temperature of 10.6 °C, selected on the basis of DB viscosity measurements). In this work, PBPs meeting pipeline transportation specifications are prepared by visbreaking and/or solvent-deasphalting of bitumen followed by dilution with 32–47 wt% less diluent than the corresponding unprocessed DB. Public concern about environmental risks associated with spillage of emerging PBPs during transportation has spurred investigations of these products’ interactions with water. With little currently known about their aquatic behaviours, we evaluate the emulsification and dispersion tendencies of pipeline-transportable PBPs after mixing these with fresh water following a reported protocol, and compare these results with those for DB, bitumen-derived synthetic crude (SC) oil, and conventional crude (CC) oil. The characteristics of floating water-in-oil emulsions are shown to depend upon the oil’s asphaltene content and thermochemical process history. At high mixing energy, dispersed oil content within the water column is seen to increase with oil resin-to-asphaltene ratio. In the aquatic system employed, oil content of the water column is greatest for SC, followed by solvent-deasphalted products and DB, followed by only-vis-broken product and CC. These results may aid in the development of oil spill behaviour models and response plans needed for transporting PBPs.

Determination of stability of high-viscosity marine fuel from the point of colloid chemistry concept of oil disperse systems and the need for inclusion of this parameter in the current requirements are expounded. High-viscosity marine fuels produced from residual fuel oil, visbreaking residue, and catcracking light gas oil were taken as the objects of the study. The stability of the obtained samples was determined via xylene equivalent. Also determined was the effect of dispersing additives based on hydroxyethylated amines and alkyl naphthalenes on the stability of the obtained samples of high-viscosity marine fuels.

Solvent deasphalting and visbreaking are two important technologies in the development of processes for partial upgrading of oilsands-derived bitumen to improve oil fluidity for pipeline transport. This work investigated the impact of the process sequence, solvent deasphalting followed by visbreaking (SDA-Vis) compared to visbreaking followed by solvent deasphalting (Vis-SDA). Thermal conversion during visbreaking was performed at 380 °C for 85 min, and solvent deasphalting was performed with n-pentane. Using this combination of processes in either sequence changed bitumen from a viscosity-limited fluid to a density-limited fluid with respect to pipeline specifications. The density and viscosity of the oil products from SDA-Vis and Vis-SDA were comparable. It was found that SDA-Vis achieved 2 wt % higher liquid yield than Vis-SDA. Conversely, Vis-SDA produced an oil product with higher hydrogen to carbon ratio compared to SDA-Vis. This difference could be explained in terms of hydrogen transfer during the...

The interaction of hydrogen peroxide aqueous solutions with crude oil and high-boiling refined products, such as fuel oil and vacuum gas oil, in the presence of an oxidative cracking catalyst in the form of iron oxide nanosized particles is studied. This study is aimed at modeling processes occurring in the case of using hydrogen peroxide solutions in the catalytic cracking of crude oil. It is found that, in the presence of iron particles, the reaction of hydrogen peroxide decomposition causes the cracking of petroleum hydrocarbons. This process may be accompanied by reduction in the viscosity and density of crude oil and refined products. The reaction of catalytic cracking performed under these conditions leads to a marked increase in the fraction of light hydrocarbons in the composition of crude oil and high-boiling refined products.

Thermal cracking processes such as visbreaking are used in the petroleum industry to reduce the viscosity of heavy feedstocks, such as atmospheric and vacuum residues, without forming coke or unstable asphaltenes. Thermal cracking offers a potential method to reduce the viscosity of heavy oils and bitumen, enabling their pipeline transportation with less solvent addition. Viscosity is the most important property for transportation of crude oils, but this property also has a highly non-linear dependence on temperature and composition. In this work, we used a lumped-kinetic model, based on boiling point pseudo-components, coupled with a fluid property model, to correlate the viscosity of two heavy oils subjected to thermal cracking reactions at different severities, and assess the impact of the chemical transformations on the behavior of the heaviest fraction. The properties of these pseudo-components were estimated by validated correlations, and tuned with experimental values. By assuming that after the reactions these properties remained invariable in each boiling point pseudo-component, we could estimate the viscosity of the liquid products from the recombination of these individual properties using mixing rules available in literature. The results indicated that the vacuum residue fractions (>524 °C) undergo chemical transformations that alter their fluid properties. By using adjusting factors dependant on conversion, we were able to make estimations of viscosities at different temperatures with absolute average deviations lower than 25%.

Catalytic steam cracking (CSC) of heavy hydrocarbons is seen as an alternative for further improvement upon conventional thermal cracking performance. In this work, upgrading of an industrial deasphalted vacuum residue via CSC was assessed in a bench-scale pilot plant resembling a visbreaking unit. The performance of a 400 ppm of Ni and 300 ppm K ultradispersed catalyst (UDC) formulation previously used for CSC of vacuum residue was evaluated for this nonasphaltene containing fraction. Reactivity experiments were conducted at temperatures within 435–445 °C and liquid hourly space velocities (LHSV) of 3–5.5 h–1 and operating pressure of 300 psig. A preliminary reactivity evaluation using isotopic water spanning temperatures between 423 and 445 °C was carried out to determine the conditions at which water splitting was occurring. Finally, lumped kinetic modeling including asphaltenes generation in the process was evaluated, and results were compared with previously reported thermal cracking experiments. Ope...

In this short communication, vacuum residue, bitumen, and pyrolized fuel oil were analyzed using matrix-assisted laser desorption/ionization – time of flight (MALDI-TOF) analysis to investigate the molecular weight distribution (MWD) variation of heavy oil during visbreaking. The visbreaking of vacuum residue was carried out at 350 °C, 400 °C and 450 °C. Vacuum residue products were studied based on MWD obtained by MALDI-TOF analysis. The separation of MWD was carried out in 8 sections, and each area of the range was calculated. According to our study, the cracking reaction dominated, even though condensation and polymerization were carried out simultaneously. It was noted that the relatively high molecular ranges of 3 and 4 were shifted to the light molecular range of 2. The MWD separation method obtained by MALDI-TOF is a potential analytical tool for investigating the MWD variation of heavy oil.

In this work, the fouling behaviour of thermally processed bitumen products obtained by visbreaking was studied. The feedstock was prepared by blending raw oil sands bitumen with 15 vol% hydrotreated light oil (HLO). The visbreaking products obtained at different pitch (525 °C + fraction) conversions were characterized and tested for fouling tendency. Test results showed that the fouling tendency linearly increased with total olefin content in visbreaking products. To further investigate the separate contributions of olefins and asphaltenes to fouling tendency, a selected visbreaking product was distilled into an olefin-rich 280 °C − fraction and a “heavy” 280 °C + fraction to avoid the loss of lighter fractions during the deasphalting process. To minimize the effect of interactions between olefins and asphaltenes on the fouling tendency, the 280 °C − fraction was hydrotreated and the 280 °C + fraction deasphalted. The deasphalted samples with different olefin contents and the hydrotreated samples with different asphaltene contents were obtained by blending the processed 280 °C − and 280 °C + fractions. Test results showed that deasphalting significantly reduced the fouling tendency of the visbreaking product. In the presence of olefins, asphaltenes have a significant effect on the fouling tendency of thermally processed products, whereas in the absence of olefins, the impact of asphaltenes on fouling tendency was limited. Similarly, olefins have a limited effect on the fouling tendency of visbreaking product in the absence of asphaltenes.

Bitumen partial upgrading refers to a prospective direction in the processing of Canadian bitumen where its quality is improved just enough to meet pipeline specifications. Fixed-bed hydroprocessing is an approach with the potential to achieve this objective, outside the mainstream concept of combining visbreaking and solvent deasphalting. In continuation of previous work where we examined the fitness of purpose of fixed-bed hydroprocessing to partially upgrade oil sands bitumen, in this study we investigate the stability of the hydroprocessing catalyst system when exposed to working conditions over an extended period of operation. The trial campaign was conducted in a continuous pilot plant having a fixed-bed reactor packed with a dual catalyst system. In the first part of the experimental program, conditions were scouted to find the operating window that enabled us to meet the pipeline specifications for API gravity (19°API) and viscosity (350 cSt at 7 °C). Following completion of these tests, the stability of the catalyst over time was assessed under conditions such that the desired product quality was met. It was established that on-specification partially upgraded bitumen could be produced at conditions that permitted the attainment of residue (525 °C+) conversion levels of nearly 50%, with hydrogen consumption levels of 900–1000 scf/bbl. The catalyst system was stable over 1096 h of continuous operation (6.5 weeks), yielding on-specification product, but this was accompanied by a visible pressure drop buildup in the reactor. Characterization of the on-specification product showed increased yields of quality middle distillates and vacuum gas oil fractions.

36 vacuum residual oils, obtained from all available groups of crude oils in the world along with their deasphalted oils and their asphaltene fractions have been investigated in this work. Correlations were derived which show that the vacuum residual oil bulk properties density, Conradson carbon content, and viscosity correlate with residual oil hydrogen content, H/C atomic ratio, the fraction of aromatic carbon, saturate, and asphaltene content. It was found that the VRO metal (Ni + V) content was almost evenly distributed between the maltene and the asphaltene fractions. The data in this work presented contradictory facts about the molecular weight of the VRO asphaltene fractions. The simulation distillation data (ASTM D-7169) and Goosens’ correlation support the statement of Mullins et al. that the asphaltene fractions may have molecular weight of about 750 g/mole. The atmospheric residue physical distillation data (ASTM D-5236) and Riazi’s boiling point distribution model, however support the statement that the asphaltenes are concentrated in the higher boiling point, higher molecular weight VRO fractions. The higher the aromaticity of a heavy oil, the higher its viscosity is. Since the asphaltenes are the most aromatic compounds in a heavy oil their influence on the heavy oil viscosity is the biggest among all other heavy oil constituents. The converted vacuum residual oils (from visbreaking and residue ebullated bed H-Oil hydrocracking) demonstrated lower dependence of viscosity on the asphaltene content. This could be a result from decreasing of the dimensions of the macro-structure of the converted asphaltene molecule.

During start-up operations of the new residue ebullated bed H-Oil hydrocracking unit in the LUKOIL Neftohim Burgas refinery oil incompatibility was registered in the process of production of heavy fuel oil. Тhat was the reason for obtaining high sediment off-spec heavy fuel oil product. The oil incompatibility was observed in the process of blending of high saturate, low asphaltene, high colloidal stability H-Oil unconverted vacuum residue with the high aromatic, and relatively high asphaltene visbroken residue. The use of antifouling additive was found to decrease the sediment level in the heavy fuel oil. However, it was not capable of reducing the heavy fuel oil sediment content after chemical and thermal artificial aging of the fuel oil. Considerable amount of high aromatic fluid catalytic cracking heavy cycle oil was needed to reduce the off-spec heavy fuel oil sediment content to the specified max. limit of 0.1% sediments. After deasphaltization of the visbroken residue with n-heptane and blending of the visbroken deasphalted oil with the H-Oil unconverted vacuum residue in a ratio of 1:1 the sediment content of the heavy fuel oil blend dropped from 2.5% to 0.01%. This suggests that the lower solubility of the visbroken residue asphaltenes in the high saturate H-Oil unconverted vacuum residue was the reason for the oil incompatibility during the production of off-spec heavy fuel oil in the LUKOIL Neftohim Burgas refinery when both the H-Oil residue hydrocracker and the visbreaker were in operation.

Thermal conversion of oilsands bitumen at 400 °C was investigated to gain a better understanding of temporal changes in liquid properties. The work approximated a mild thermal cracking (visbreaking) process with run-lengths extending into the coking region. Reaction progress could be divided into three main regimes: (I) stable visbreaking, (II) coking visbreaking, and (III) coking. In addition to observations anticipated from the literature, the work revealed aspects of the reaction progression that was not fully appreciated before. Stable visbreaking with minimal formation of coke had a “productive” period during which viscosity decreased, while asphaltenes content and gas yield were unchanged, followed by an “unproductive” period during which the viscosity, asphaltenes content, and gas yield all increased. After the onset of precipitation of solids, the solids (“coke”) yield increased and the asphaltenes content in the liquid decreased, but the viscosity increased. The origin of increased viscosity was ...

The modified regular solution (MRS) model for asphaltene precipitation was extended to visbroken bitumen products based on data from an Athabasca bitumen that was thermally cracked in a lab-scale flow-through visbreaker at five different temperatures and residence times. The thermal conversion for each visbroken product was calculated based on SimDist data. The feed and each product were characterized into 5 pseudo-components (distillates, saturates, aromatics, resins, and asphaltenes) using spinning band distillation and SARA assays. Properties required for the model (molecular weight, density, and solubility parameters) were measured or estimated for each pseudo-component. New correlations were proposed for the distillate fraction properties as a function of conversion and the existing correlations for the SARA fraction properties were updated. The remaining model inputs are the feedstock composition, the feedstock pseudo-component properties, and conversion. The MRS model was able to match the measured asphaltene precipitation yields from visbroken heavy residues and visbroken whole oils with average absolute deviations of 1.2 wt% and 0.4 wt%, respectively. The model validity is currently limited to Western Canadian heavy oils derived from the same source region as the oil sample used for this study.

An unexpected ignition of pyrophoric iron sulphide deposits took place in the fractionator of a Visbreaker unit. The distillation column had been chemically decontaminated prior to the event. The investigation of the event leads to conclusions concerning chemical decontamination limitations in vessels in coking service. Based on the lessons learned from this case, a prioritization of manual vessel cleaning works in coking service is proposed.

Nine vacuum residual oils were characterized and eight blends of them were processed in the LUKOIL Neftohim Burgas commercial visbreaker unit. It was found that at constant content of about 8 vol.% of the fraction boiling up to 360 °C (diesel cut) in the visbroken residue the visbroken residue viscosity correlated with the vacuum residual oil visbreaker feed viscosity with a squared correlation coefficient R 2 > 0.98. By application of correlation analysis and intercriteria analysis the vacuum residual oil feedstock parameters which have statistically meaningful impact on conversion to product boiling below 360 °C were found to be vacuum residual oil sulfur and hydrogen content, and solubility power of maltenes. The results obtained in this work are consistent with those obtained from other groups, even for other types of vacuum residue processing like ebullated bed hydrocracking. The vacuum residual oils which contained more resinous-asphaltenic materials formed more asphaltenes in the process of thermal conversion. The vacuum residual oil viscosity increment with increasing of asphaltene content for the straight run vacuum residual oils can be described by a second order polynomial. The secondary vacuum residual oils — the visbroken vacuum residual oils exhibited a lower than straight run residual oil dependence of the residue viscosity increment on increasing of the asphaltene content.

Electron beam technology, as a promising energy-efficient process, is used as a new treatment for ultra-heavy asphaltic petroleum fluids. Over the past few decades, heavy oil resources have been recognized to be among the most abundant sources of energy. However, extraction, transportation, and processing problems of these fluids still remain to be a challenge in the petroleum industry. The contribution of these hydrocarbon resources to the energy market has been impacted by the fact that the conventional upgrading and visbreaking methods demand a considerable energy investment. In this paper, we coupled electron beam irradiation with conventional thermal processing methods to find an energy-efficient way of improving unfavorable properties of heavy asphaltic hydrocarbons. Electron irradiation was observed to improve the viscosity reduction process by a factor of 30% compared to thermal treatment. Energy transfer process becomes more efficient in radiation-induced reactions, which results in an intensified cracking process. The role of complex asphaltene structures on radiation thermal cracking was investigated by using hydrocarbons with high and low asphaltene content. Our results showed that in samples with high asphaltene content, electron radiation impacts the reaction mechanism of the thermal cracking process. In fact, high energy electrons interact with aromatic structures of asphaltene molecules, resulting in products with a different hydrocarbon component distribution and time-stability properties, as opposed to the simple thermal cracking case. On the other hand, experiments showed thermal and radiation thermal cracking processes follow a similar reaction mechanism for hydrocarbons of low asphaltene content.

This study compared various thermal cracking processes for Athabasca oil sand bitumen according to the relationship between vacuum residue (VR) conversion and the product yield for each process, using reported data. The conversion was defined as the fraction of VR that was converted to lighter products. The conventional processes examined were visbreaking, delayed coking, and fluid coking, and the developing processes were high conversion soaker cracking (HSC), heavy to light (HTL), IYQ, Eureka, and supercritical water cracking (SCWC). HSC and SCWC were higher severity visbreaking-type processes with conversions of 0.49 and 0.39–0.50, respectively. HTL and IYQ (recycle) were lower severity fluid coking-type processes with a conversion of 0.52. IYQ (once through) and Eureka showed the highest conversions (0.62–0.68). Supercritical water (SCW) upgrading was operated experimentally at higher severity, with a conversion of 0.64, and showed the highest yield of distillate product (DP) among all thermal crackin...

The low-temperature visbreaking of Canadian oilsands-derived bitumen was investigated. The objective was to determine the extent to which the fluidity of the bitumen can be improved by less-severe thermal conversion than normally employed industrially, while, at the same time, maintaining a high liquid yield. Most of the experimental work was conducted in the temperature range of 340–400 °C, although some data were also obtained at lower temperatures. It was possible to limit gas and coke formation and obtain a 96–97 wt % liquid yield, while decreasing the bitumen viscosity from ∼100 Pa s to 1 Pa s (measured at 40 °C). More remarkable was that viscosities of ∼3 Pa s could be obtained by just heating the bitumen to either 360 or 380 °C and then cooling it. The most plausible explanation for the rapid decrease in viscosity during low-temperature visbreaking was that there was a decrease in the effective volume fraction of the colloidal fraction. The viscosity change over time at constant temperature was com...

Thirteen vacuum residual oils originating from Russia, Middle East, Asia, and South America were thermally cracked in a modified high-temperature–high-pressure batch autoclave reactor. It was found that the colloidal stability of the vacuum residual oils expressed by S-value was the dominant factor that affected the residue thermal reactivity. SARA analysis data of the residual oils were confirmed to contain insufficient information about residue thermal reactivity and colloidal stability. It was found that the higher the colloidal stability of a residual oil the lower residue thermal reactivity and the steeper colloidal stability reduction during thermal conversion. The asphaltene solubility was found to linearly decrease with the increase of the thermal conversion, while the maltene solubility power did not always decrease with the increase of the thermal conversion for the studied residual oils. Having in mind that the ebullated bed residue hydrocraking H-Oil process is also based on thermal conversion the properties of commercial straight run Urals vacuum residue (UVR), visbreaker residue obtained by thermal cracking of UVR (UVBR), and ebullated bed hydrocracking (H-Oil) unconverted residue were investigated. It was found that asphaltene solubility lowered linearly with increasing of conversion regardless of the process: visbreaking or ebullated bed hydrocracking. The maltene fraction average molecular weight seems to decrease with the increase of the residue thermal conversion processes visbreaking and ebullated hydrocracking as the asphaltene average molecular weight does for the same processes. It was found that the atmospheric gas oil fraction from visbreaker has no negative effect on residual oil colloidal stability while the vacuum gas oil fraction has negative impact on residue stability in both visbreaker and H-Oil unconverted residual oils. The data generated in this work study suggest that the asphaltene solubility has a bigger impact on the residual oil colloidal stability than the maltene solubility power.

New asphaltenes are formed during the thermal conversion of heavy oil. When new asphaltenes are formed from deasphalted oil, it erodes the conversion advantage provided by solvent deasphalting prior to visbreaking. The postulate that asphaltenes formation is caused by free radical addition reactions was evaluated. Indene was employed to exacerbate asphaltenes formation during thermal conversion of deasphalted oil at 400 °C. Evidence was provided that indene was involved in addition reactions with itself and with deasphalted oil to produce new n-pentane insoluble material. Whether indene induced increase asphaltenes formation, or whether it formed addition products with the deasphalted oil was not resolved. Self-reaction of indene at 400 °C resulted in extensive formation of n-pentane insoluble material. Formation of n-pentane insoluble material was reduced in mixtures with indane and naphthalene. Using these model systems the presence and nature of addition products was determined. The reported thermal conversion of indene was consistent with reaction chemistry based on molecule-induced homolysis, free radical addition, and propagation / termination by hydrogen transfer. The prevalence of addition reactions and the importance of hydrogen transfer reactions were highlighted, which have implications for modelling reaction chemistry describing thermal conversion of heavy oil.

cited By 3; International audience; Silicon species are becoming emergent contaminants in the oil and gas industry due to their severe poisoning effect on the hydrotreatment (HDT) catalysts. Using an experimental pilot plant, fresh and representative samples of PDMS degradation under thermal cracking of hydrocarbons were produced. To follow the evolution of silicon species, the gas fraction was immediately analyzed by GC/TOFMS after the production and also after 4 months of storage at 4 C. Cyclic siloxanes (Dn) as the major products of PDMS thermal degradation were characterized in the gas phase but these compounds are mainly present in the liquid fraction. Five volatile silicon compounds belonging to the families of silanes, siloxanes and silanols were characterized and quantified in the thermal cracking samples depending on the operating conditions applied in degradation tests. Under coking or visbreaking conditions (long residence time, absence of steam), silanes and siloxanes were preferentially formed. Under evaluated steam cracking conditions (short residence time and presence of steam), trimethylsilanol (TMSOH) was mainly produced by the hydrolysis of PDMS. The formation of the linear siloxane (L2) after several month of storage at 4 C by the self-condensation of TMSOH was also observed. The suspected poisoning effects of these molecules were discussed and could explain the deactivation of catalysts taking place in the refining of the light petroleum cuts. The new identified volatile silicon compounds could affect the performance of the catalyst by the reaction of hydroxyl groups potentially present at the surface of the support with reactive silicon molecules, more specifically silanols. © 2013 Elsevier Ltd. All rights reserved.

Oil resources similar to WTI and Brent crude oils are dwindling, so heavy and extra-heavy crude oils, and bitumen must be used to meet the growing demand for fuels. The vast majority of the world's refineries are not suitable for processing these types of feed stock, so upgrading processes are required to make synthetic crude oils from those resources compatible with the equipment installed. By its viscosity Castilla crude oil is not classified as an extra-heavy crude oil, as even on surface it flows. However, it has 45.6 wt.% of vacuum bottoms and high concentrations of Conradson Carbon (CCR of 34 wt.%) and metals (nickel and vanadium content of 928 ppm) within it. This article presents various alternatives for the upgrading of the crude Castilla, using as raw material crude oil free of lights (199 °C+), reduced crude (370 °C+) and vacuum bottoms. The technologies used in the studied scheme were visbreaking (VBK), delayed coking (DC), solvent deasphalting (DAF), hydrotreating and distillation. The studies were conducted at pilot plant scale and the analysis of the products was done using standard techniques such as ASTM. Among the outstanding results we have the operational scheme of the vacuum bottoms Visbreaking, but this is not a typical Visbreaking process because the coke production was 8.2 wt.%. A furnace with some characteristics of a DC furnace, and a pair of soakers that function as coking drums should be used to avoid coke deposition within the internal walls of the coils. This is an innovative technology that sits between visbreaking and delayed coking.

As one of the important in‐situ upgrading technologies, catalytic aquathermolysis has attracted worldwide interest for heavy oil exploitation recently. Aiming to upgrade and visbreak a kind of super‐heavy oil, we have synthesized a new type of catalyst — aromatic sulfonic copper to process it. The experimental results show that, using 0.2 wt.% catalyst and 25.0 wt.% water at 280 °C for 24 h, the viscosity of oil sample could be decreased by 95.5%, with 13.72% in the conversion of heavy content to light content. Furthermore, the structure and group compositions of heavy oil were characterized by FT‐IR, GPC, EL, 1 H NMR and GC–MS. It is found that the catalyst could improve the pyrolysis of heavy oil, and remove some heteroatoms (S, O and N) in its molecules, which finally led to the upgrading and visbreaking of the oil. Additionally, in view of the low‐cost for synthesis and simple preparation of this technique, it is likely to have some good application prospects.

The fluid behavior of asphaltenes at elevated temperatures impacts coke formation in a number of hydrocarbon conversion processes, including visbreaking and delayed coking. In this study, the asphaltenes from a number of sources, namely, a vacuum residue, a petroleum source rock (Kimmeridge clay) bitumen obtained by hydrous pyrolysis, and bitumen products from a sub-bituminous coal and pine wood obtained by thermolytic solvent extraction using tetralin, have been characterized using high-temperature proton nuclear magnetic resonance (1H NMR), and the results correlated with those from small-amplitude oscillatory shear rheometry. Further for comparison, the coke (toluene insolubles) obtained from visbreaking the vacuum residue was also characterized. All of the asphaltenes became completely fluid by 300 °C, with hydrogen being completely mobile with coke formation, identified as a solid phase, not occurring to a significant extent until 450 °C. Extremely good agreement was obtained between high-temperature 1H NMR and rheometry results, which confirmed that the asphaltenes were highly fluid from 300 °C, with initial signs of resolidification being observed at temperatures of around 450 °C. During softening, extremely good correlations between fluid hydrogen and phase angle were obtained as the asphaltenes softened. The toluene insolubles however did contain some fluid material; thus, it cannot be regarded as strictly solid coke, but clearly, with increasing temperature, the fluid material did convert to coke. Under actual process conditions, this fluid material could be responsible for coke adhering to reactor surfaces.

Summary Previously, nuclear-magnetic-resonance (NMR) carbon-type-analysis data were used to develop a mathematical model of mild thermal conversion (visbreaking) of Athabasca bitumen (Chan et al. 2006). In that work, the major reaction pathways followed during visbreaking were identified. This approach is being extended in the current work to model the visbreaking behaviour of five different oils from different geographical locations around the world. This paper shows the correlation of residue conversion with the contents of different carbon types for five heavy oils from four continents. During visbreaking runs, operators intend to maximize process yields. This is achieved through increasing process severity by raising temperature. However, if the temperature is too high, coke forms. This maximum temperature varies with different crude oils; therefore, as refinery feedstock composition changes, so does the onset of coking temperature. Coke is a hydrocarbon material that has low hydrogen content and is insoluble in the oil. Consequently, this precipitates in the reactor, eventually causing an unscheduled unit shutdown. We have found that contents of specific carbon types in the feed oils correlate with coke formation. This correlation allows prediction of the quantities of coke that will form under the chosen visbreaking (mild thermal) conditions and the "maximum" quantities of coke that would form under coking (severe thermal) conditions.

Diesel oil component and aromatized extract with a high sulfur content have been obtained by extraction purification of mixtures of catcracking and visbreaking light gas oils using N,N-dimethyl formamide in the presence of hexane. The extract can be used for production of technical-grade carbon.

Several models have been reported in the literature for thermal cracking of petroleum residues. Most of these models are either highly empirical or first principles based models requiring detailed analysis of the feedstock. The present paper is an attempt to put forward a critical appraisal of various published models. The authors have also generated the experimental data on a batch reactor for different feedstocks, and multi-lump parameter models (reported elsewhere) have been developed with the generated data. Three different models for prediction of experimental yields in terms of gas and distillate fractions (i.e. kerosene, LGO and VGO) have been critically evaluated in the light of experimental data.

Finding new economic means of upgrading residuals is becoming increasingly important. In this work, the upgrading of Arabian Light vacuum residue under asphaltene stability limit by steam catalytic cracking using unsupported ultra-dispersed (UD) alkali and a non-noble transition metals catalyst is investigated in a continuous open tubular reactor pilot plant. The experiments are conducted with K/Ni UD catalyst under 260 psig at process temperatures of 430–445 °C and LHSV of 5–10.5 h–1. Experimental results showed a relative increase in the residual oil conversion of 13% by Aquaprocessing at the minimum asphaltene stability limit when compared to conventional thermal cracking. With the use of O18 labeled water, it is confirmed that the UD catalyst during reaction is capable of dissociating water into hydrogen and oxygen radicals at near visbreaking conditions.

The drawbacks of the planned version of the product separation block are examined on the example of a visbreaking unit at a Russian oil refinery. The causes of its inefficient operation and rapid coking of the equipment are determined. The process solutions to improve the operation of this block which were developed and implemented are presented.

Different aspects of visbreaking with a soaker and coil were examined. The advantages and disadvantages of different methods of turbulization and chilling and different types of heat-exchange equipment were analyzed. The possibility of totally stripping hydrogen sulfide was established. The effect of different factors on the stability of the visbreaking residue was examined. Ways of efficiently utilizing visbreaking residue were demonstrated.

A new visbreaking unit with output of 1.5 million tons a year in vacuum resid was started up at Salavatnefteorgsintez Co. A separate reaction chamber (soaker) is provided in the unit for increasing the degree of feedstock conversion and reducing coking of furnace coil tubes. To increase takeoff of gasoil cuts, the unit is equipped with a vacuum block. Heavy and light vacuum gasoils are used for preparation of type M-100 atmospheric resid.

The possibility of converting a combined delayed-coking unit to operating in conditions of mild thermal cracking (visbreaking) of petroleum resids is examined. Major technical and process solutions that ensure the maximally efficient use of the existing equipment are proposed. The possibility of obtaining boiler fuel with a maximum residual hydrogen sulfide content of 2 ppm is demonstrated. Cost effectiveness is ensured by a significant increase in the volume of refined petroleum resids.

The relationship between the structure and stability of the visbreaking product of Venezuela extra heavy oil has been studied. The number of resin layers adsorbed to asphaltene is proposed to describe the colloidal stability of Venezuela heavy oil and its visbreaking product. The results show that the colloidal stability of the visbreaking product is inferior to Venezuela heavy oil. The factors influencing the storage stability of the visbreaking product have been studied by analyzing the changes of kinematic viscosity, total acid number (TAN), weight loss, ratio of resins/asphaltenes, as well as free-radical content of visbreaking samples sealed and exposed to air or nitrogen for 90 days. It is found that the storage stability of the visbreaking product is influenced by oxidative condensation, evaporation, and non-oxygen condensation, among which oxidative condensation is the most significant factor. The free-radical reactions do not terminate after the thermal reaction, and the content of free radicals ...

To identify hydrocarbons that might be sensitive indicators of coke formation in visbreaking, experiments have been conducted on a vacuum residue at 410 °C with residence times of up to 60 min in a...

In a refinery, crude petroleum oil is distilled in an atmospheric column to separate fuel gases and distillates. Reduced crude oil (RCO) from the atmospheric distillation unit is further distilled under a vacuum, yielding varieties of distillates like vacuum gas oil and light to heavy viscous distillates. In a typical lubricating base oil–producing refinery, viscous distillates from intermediate to heavy are available from such a unit. Highly viscous distillate is also recovered from the vacuum residue. Solvent extraction takes place (Sequeira and Dekker, 1993c, p. 81; 1993b, p. 153) next to selectively dearomatize the distillates to yield high viscosity index (VI) oil. In order for the pour point to be improved, selective removal of paraffin wax is carried out in a solvent dewaxing unit. Finally this dewaxed oil is selectively hydrogenated to remove unwanted sulfur, nitrogen, and oxygen and also for improving color. Though modern catalytic aromatic saturation and dewaxing (Sequeira and Dekker, 1...

Adsorption of virgin and thermally cracked vacuum residue from Athabasca bitumen was recently reported, using synthetic macroporous kaolin as adsorbent. Following that work, this study addressed the adsorption properties of virgin vacuum residue from Athabasca asphaltenes and thermally cracked products from these over different solid substrates. Synthetic (macroporous kaolin) and natural reservoir materials (siltstone and montmorillonites) are the adsorbents studied. Thermally cracked asphaltenes (mild visbreaking process) were used as proxies for the organics that remain downhole after a thermally production process. Adsorption experiments were carried out with toluene solutions of the studied adsorbates, monitored via UV−vis spectrophotometry. The findings showed that asphaltene from Athabasca virgin vacuum residue and thermally cracked products derived from it interact to different extents with solid surfaces. Evidence suggested that molecular size of these fractions does not limit their adsorption ove...

Thermal visbreaking of inner Mongolia oil sand bitumen was conducted at several temperatures for different lengths of time in the laboratory. The viscosity of the thermally-treated oil was reduced dramatically with thermal treatment under the condition of adding 0.3 wt% anti-coking agent, the oil sand bitumen reacting at 410°C and 45 min. The kinematic viscosity (100°C) of visbreaking oil is reduced to 138.25 mm2·s−1 and the qualities of it are conformed to 7# Chinese Standard for Fuel Oil, which can directly be regarded as product.

The production of modified heavy molecules via thermal cracking (visbreaking) and their corresponding adsorption over macroporous silica–alumina, such as kaolin, is described. The characterization of cracked products in terms of hydrocarbon type SARA distributions and stability indexes (P value) is discussed. Improving the properties of visbreaking products after adsorption over kaolin adsorbent with the quantification of organic adsorbates is presented. Preliminary insights on the nature of those organic adsorbates are described. The feasibility of including an adsorption step after thermal cracking for process improvement is demonstrated in this article.

The vacuum residue prepared from Athabasca bitumen was heated at 380 °C for up to 5.5 h under vis-breaking conditions. The level of conversion was indicated by weight loss due to generation and removal of light ends from thermal cracking reactions. Classical molecular parameters that are commonly applied to indicate the level of thermal maturity of petroleum source rocks during burial maturation have been investigated toward indicating the extent of bitumen conversion under vis-breaking conditions. The molecular parameters known to monitor chemical reactions such as isomerization, carbon−carbon bond cracking, and aromatization showed strong correlations with the level of conversion during vis-breaking. The reaction mechanisms based on simple precursor−product relationships appear inherently more complex when quantitative molecular data are considered. For example, generation of Tm influences the behavior of Ts/(Ts + Tm), while changes in the triaromatic steroid parameter C20/(C20 + C28S + C28R) is control...

In order to provide a solution for refineries having limited catalytic reforming capacity, a process scheme for incorporating most of the low octane heavy hydrotreatment and visbreaker naphthas into diesel is presented in this paper. This scheme involves blending the visbreaker naphtha with the feed to the diesel hydrotreatment units, processing this blend at the usual conditions for diesel hydrodesulfurization and changing the cut point in the diesel stabilizer. The proposed scheme was tested in a pilot plant, using blends of visbreaker naphtha and straight run gas oil as feedstock. The proportion of visbreaker naphtha was selected according to the production of this naphtha and of straight run gas oil in a typical refinery. The hydrotreated product was stabilized at different cut points and a target cut point was selected for maximum diesel production, meeting all the product specifications. This scheme was applied at a refinery having one visbreaking unit and two diesel hydrotreatment units, resulting in an increase of 6-7% in diesel production.