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The inlet temperature of the Vacuum Gas Oil (VGO) hydrotreating reactor of a refinery is analyzed with the integration of multiple series reactors and hydrogen network considered. The effect of the inlet temperature (T1) on hydrogen sinks/sources and the product output is analyzed systematically based on the simulation of the series reactors, including VGO hydrotreating reactor, hydrocracking reactor, fluid catalytic cracking reactor and visbreaking reactor. The general relation between the Hydrogen Utility Adjustment (HUA) and multiple pairs of varying sinks and sources is deduced, and correlations between varying streams and T1 are linearly fitted. Based on this, the quantitative equation between HUA and T1 is derived, and corresponding diagram is constructed. The T1 corresponding the minimum hydrogen consumption is identified to be 345 °C.

The review deals with extraction refining of straight-run diesel fractions, atmospheric gasoil, gasoils from secondary oil refining processes (decelerated coking, visbreaking, catalytic cracking), and light and heavy vacuum gasoils to remove heteroatomic sulfur- and nitrogen-containing compounds, polycyclic arenes, and resins using selective organic solvents and extraction systems with a nonpolar solvent. Possible methods for extraction regeneration and extract application fields are considered.

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 results of the calculation of the reactivity descriptors of structurally different polyaromatic hydrocarbons (PAHs), which act as starting compounds in condensation and polymerization reactions and the subsequent formation of coke occurring on the heating of hydrocarbon raw materials in the course of visbreaking in tube furnaces are presented. The activation energies and preexponential factors of chemical reactions of hydrogen atom removal from PAH molecules, which simulate the local environment of a coke layer, as a result of their interaction with the radical ⋅CH3 were calculated using quantum chemical methods.

Performance predictions of the In-Situ Combustion (ISC) process is a challenge as it involves complicated chemical reactions, fluids movement, phase changes, and heat and mass transfer. This study investigates how oil type and water presence can affect the ISC performance, based on using a combination of combustion tube and Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA/DSC) experiments. Combustion tube experiments were conducted with two different crude oil without water (Swi = 0%) and with the presence of water (Swi = 34%). Experimental conditions were kept constant (3 L/min air injection rate and 100 psig pack pressure) for all four experiments conducted with two different oil samples. To determine the chemical reactions that occurred during combustion tube experiments, the initial crude oil samples and their Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractions were subjected to TGA/DSC experiments under air injection at two constant heating rates with and without water addition. Because two heating rates were observed during combustion tube experiments, 5 °C/min was used to represent the slow heating region (Steam Plateau, Evaporation and Visbreaking) and 20 °C/min was used to mimic the rapid heating region (Cracking Region and Combustion Zone). To better understand the complicated mutual interactions of functional groups in crude oil, TGA/DSC experiments were repeated on normal-decane (an alkane), decanal (an aldehyde), decanone (a ketone), and decanol (an alcohol) which represent the low temperature oxidation (LTO) products. Note that these chemicals have a constant carbon number (C10). The combustion tube experiments showed that Oil 1 was able to burn for both conditions (with and without water), while Oil 2 could only sustain combustion with water. To determine the reason for this difference, the burning behavior of the crude oils and their individual SARA fractions with and without water additions was studied through TGA/DSC experiments. At the high heating rate (20 °C/min), heat generation does not vary for both crude oil samples. However, at the low heating rate (5 °C/min), Oil 1 generates a higher amount of energy at high temperature oxidation (HTO) zone. We observed similarities between the decanone (a ketone) burning behaviors with aromatics fractions for Oil 1 which indicates that the aromatics fraction may contain ketone functional groups as LTO products. Upon burning, ketones generate higher energy than any LTO products. Therefore, Oil 1 may have functional groups in its structure more like ketones which promotes its combustion more than Oil 2. While presence of water does not change the burning behavior of Oil 1, we observed that the aromatics fraction of Oil 2 in the presence of water generates components similar to decanol (an alcohol) burning behavior. Note that alcohols generate more heat than aldehydes upon burning which explains the enhancement of Oil 2 burning behavior in the presence of water. However, aldehydes produced less energy than ketones. As a result, the combustion performance of Oil 2 was poorer than Oil 1. These results suggest that the chemical structure of the aromatics fraction is critical for the success of ISC. Water and aromatics fraction interaction at elevated temperature favors ISC reactions.

In view of the worsening quality of crude oil, the use of unconventional petroleum feedstocks (heavy oils, bitumens, residues, etc.) in processing is becoming increasingly important. The processing of heavy oil feedstocks (HOF) requires the development of new effective techniques that will lead to an increase in the yield of light fractions, suppression of coke formation, and saturation of liquid products with hydrogen. At the same time, the capital and operating costs of the process should be minimized because the cost of production and transportation for HOF is several times higher than for light and middle oils. The present review summarizes the results of studies of the catalytic steam cracking of HOF—a potential alternative to conventional HOF upgrading based on carbon rejection (thermal cracking, visbreaking, catalytic cracking) or hydrogen addition (hydrocracking). The main differences of this process from HOF upgrading with water (aqueous pyrolysis in sub- or supercritical water), the peculiarities of the catalytic steam cracking depending on the process conditions and the type of catalyst, and possible mechanisms of water participation in the process were discussed.

Initiator is used in the aquathermolysis visbreaking of heavy oil combined with catalyst and other additives. The results show that viscosity reduction ratio goes up from 61.4% to 72.7% after adding 0.2 wt% di-tert-butyl peroxide at 220°C. Initiator is an effective addictive and can further enhance the level of thermal cracking, surprisingly leading to a decent viscosity reduction ratio 69.0% under a relatively low reaction temperature of 150°C. Oil samples are analyzed before and after the reaction, with results showing that the contents of saturate and aromatic increased, while the contents of resin and asphaltene decreased. In addition, the average molecular weight value of each component decreased after the reaction. Elemental analysis of both resin and asphaltene shows that hydrogen to carbon atomic ratio increases slightly. The contents of sulfur decreased remarkably, yet the contents of nitrogen decreased slightly. This phenomenon indicates that sulfur plays a remarkably important role during the aquathermolysis. The HAU/CA of both resin and asphaltene increases. The results above imply that with the help of catalyst and hot water, the cracking reaction of heavy oil occurs, and initiator strengthens the process. Asphaltene and resin suffer a deeper level of cracking into lighter fractions, leading to a substantial viscosity reduction and then an improvement of the flow properties of heavy oil, which also contributes to the improvement of the quality of heavy oil.

The visbreaking of heavy oil under high-pressure N2 or supercritical water (SCW) environment was experimentally investigated. Despite the difference in the reaction media, the visbreaking follows the same mechanism, that is, dealkylation and condensation of aromatics. The presence of SCW makes it possible that the visbreaking of heavy oil is transferred to the SCW phase with superior diffusivity by which the visbreaking tends to be controlled by intrinsic reaction kinetics rather than by diffusion. Accordingly, dealkylation occurring in the SCW phase, which is vital to the viscosity reduction of heavy oil, responds sensitively to the increase in reaction temperature. Being the secondary reaction of dealkylation at moderate temperatures, condensation is effectively suppressed with reduced reaction time required for dealkylation. By the introduction of SCW and the adoption of an appropriate reaction temperature, the visbreaking efficiency could be drastically improved together with guaranteed stability of v...

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.

Deterioration of the quality of oilstock makes it an urgent problem to use non-traditional hydrocarbon materials (heavy oil, bitumen, residues etc.). Processing of heavy oilstock (HOS) needs new methods that would be effective for the yields of light fractions, suppression of coke formation, and saturation of the liquid products with hydrogen. At the same time, expenses of HOS extraction and transportation are several times as high as those of light and middle oils that makes it necessary to minimize the capital and operational costs for the process. The review paper integrates for the first time the results of the studies of catalytic steam reforming of HOS as a potential alternative of the traditional processes for HOS upgrading based on decreasing the carbon content (thermal cracking, visbreaking, catalytic cracking) or on the saturation of liquid products with hydrogen (hydrocracking). Under discussion are main distinctions of the process from HOS upgrading with water (hydropyrolysis in sub- or supercritical water) as well as specific features of the catalytic steam cracking as dependent on the process parameters and catalysttype and putative mechanisms of the participation of water in the process.

The visbreaking of Canadian oil sands bitumen (OSB) and Tahe atmospheric residue (AR) with high metal and asphaltene content was studied to deepen the understanding of the utilization of ultra-inferior heavy oil. The total content of nickel and vanadium in the asphaltenes contained in Canadian OSB reaches 1300 ppm, promoting large-scale aggregation of asphaltenes. Driven by high asphaltene content of 19.3 wt% and large-scale aggregation of asphaltenes, Canadian OSB with an initial boiling point (IBP) of 500 °C exhibits rapid condensation during visbreaking. Furthermore, those asphaltenes with the highest metal content participate in condensation first, producing metallic nickel in the formed coke. By changing cutting strategy, the group composition and metal distribution of Canadian OSB can be adjusted. A viscosity reduction rate above 99 % is obtained during the visbreaking of Canadian OSB with an IBP of 350 °C, similar to the visbreaking of Tahe AR with an asphaltene content of 15.4 wt% and a total metal content of 300 ppm.

To understand the reaction behavior of heavy oil visbreaking with reduced diffusion limitation, the visbreaking of an atmospheric residual oil in the solvent of supercritical benzene (SCbenzene) was applied, followed by a reaction kinetics analysis based on a hybrid lumping with combination of boiling point distribution and group composition of oil components. The visbreaking under SCbenzene environment was found to be much faster than that under nitrogen environment, proceeding effectively even at a temperature lower to 350 °C. Although the dealkylation-based lumped reactions responsible for light component production and viscosity reduction are supposed to dominate the visbreaking, a competition between dealkylation and condensation exists throughout the visbreaking. Because of the reduced diffusion limitation to reaction kinetics, the condensation-based lumped reactions with a higher activation energy up to 306 kJ.mol−1 respond more sensitively to the variation of reaction temperature, greatly shortening the reaction time window for the visbreaking at high temperatures.

The yields of gasoline, light and vacuum gas oils, and gas fraction in thermal cracking of heavy oil residues (visbreaking) were mathematically modeled. Calculation formulas with high statistical characteristics were obtained.

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...

Refineries process a number of gas oils such as straight run gas oil (SRGO), light cycle gas oil, coker gas oil and visbreaker gas oil for producing a common gas oil pool to be used as a transportation fuel. Considering stringent sulfur standards, new strategies and design modifications are being evaluated for desulfurization of these gas oils with minimum loss of oil during the desulfurization process. In this review, developments in solvent extractive desulfurization of gas oil have been discussed from both fundamental and applied point of views. Various performance indicators used for solvent evaluation/screening in computational and experimental studies are discussed. Particular emphasis has been given on latest developments in performance evaluation of organic and ionic liquid solvents for desulfurization of SRGO and other gas oils. Various possible designs of solvent recovery section to remove solvent from raffinate and extract phases for solvent recycling have been reviewed. Various potential optio...

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.

Fracturing wastewater is often highly emulsified, viscous, and has a high chemical oxygen demand (COD), which makes it difficult to treat and recycle. Ferrate(VI) is a green oxidant that has a high redox potential and has been adopted for the efficient oxidation of fracturing wastewater to achieve triple effects: demulsification, visbreaking, and COD removal. Firstly, optimal conditions were identified to build a model for fast and efficient treatment. Secondly, wastewater treatment using ferrate oxidation was investigated via demulsification, visbreaking, and COD removal. Finally, a mechanism for ferrate oxidation was proposed for the three effects using Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The theoretical and experimental data demonstrated that the ferrate oxidation achieved the three desired effects. When ferrate was added, the demulsification efficiency increased from 56.2% to 91.8%, the total viscosity dropped from 1.45 cp to 1.10 cp, and the total removal rate of COD significantly increased to 74.2%. A mechanistic analysis showed that the strongly-oxidizing ferrate easily and efficiently oxidized the O/W interfacial film materials, viscous polymers, and compounds responsible for the COD, which was a promising result for the triple effects.

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.

Chemical characterization of heavy oil fractions is impractical because of their complexity. As an alternative, thermogravimetric analysis (TGA) provides fast and valuable information about composition of streams entering and leaving visbreaker unit in oil refineries. Deconvoluting thermogravimetric curves allows thermal-based composition of visbreaking streams to be elucidated by using pseudo-components: four for visbreaking feed and seven for visbreaking residue. In both cases, some pseudo-components explains volatilization of light substances (viz. naphtha or gasoil) under 350 °C, and three explains cracking of heavy molecules (viz. resins or asphaltenes) around 380 °C, 411 °C and 453 °C. Obtained results make it possible to define a thermogravimetric index that characterizes composition of visbreaking samples (feed and residue). This index is higher in feed than in residue, and it is higher in light samples than in heavy samples. Deconvolution of TGA curves was improved by using autocatalytic kinetic based on extended Prout–Tompkins equation.

The results of the mathematical simulation of the thermal cracking (visbreaking) of tars are reported. The methods of plotting kinetic curves were proposed for the determination of visbreaking product concentrations in a reaction mixture under given conditions. The effectiveness of the algorithms of plotting kinetic curves on a computer with specified computational resources was compared.

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.

Monitoring asphaltenes is very important with a view to optimizing visbreaking units in oil refineries. Current analyses based on selective dissolution in different solvents are slow, so new, more expeditious methods for measuring asphaltenes are required to facilitate fuel-oil production. In this work, we studied the thermal degradation of asphaltenes as the potential basis for a thermogravimetric method for their monitoring in visbreaking streams. The thermal degradation of asphaltenes occurs largely from 400 to 500 °C; the process is quite smooth in an inert environment but involves several fast mass loss events in the air. Kinetic parameters for characterizing the process were determined by using two model-free methods and the modified Prout–Tompkins kinetic equation to examine asphaltene thermolysis. Both types of methods showed the activation energy to increase during pyrolysis but to remain almost constant during cracking in the presence of oxygen or even diminish during char oxidation. Deconvoluting the thermogravimetric profiles revealed that asphaltene thermolysis in the air cannot be accurately described in terms of an n th order kinetic model because it involves some acceleratory phases. Also, thermogravimetric analyses of visbreaking streams revealed that char production in them is proportional to their asphaltene content. This relationship enables the thermogravimetric measurement of asphaltenes.

A reactor model to simulate the visbreaking process is developed. The model includes two types of visbreaking reactors: coil and soaker. For the vaporization in the reactor to be taken into account, the vapor–liquid equilibrium (VLE) is first determined, and then the reactor model is solved only with the liquid phase because thermal cracking reactions occurring during visbreaking take place in this phase. The variation of liquid and vapor flow rates are also taken into consideration. A reaction scheme based on nine pseudocomponents and kinetic expressions reported in the literature were used. It was found that VLE affects the prediction of reactor conversion depending on the feedstock and the operating conditions. The residue conversion decreases when VLE is considered, which is due to vaporization diminishing the reactor space available for performing the reactions. The model predicts greater mass fractions of gas and naphtha than the experimental values. This is because the model assumes that they are p...

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 ...

Today, many European refineries finish up with excess of low-quality thermal naphthas that are hard to be marketed and, commonly, end being absorbed by catalytic naphthas at the expense of their higher quality. In this context, we propose to investigate the suitability of co-feeding thermal naphthas, i.e. visbreaker and heavy coker naphtha, with vacuum gasoil (VGO) to the fluid catalytic cracking unit. A riser simulator reactor has been used in the experimentation and tested conditions have been: 500 and 550 °C; C/O mass ratio, 6 gcat goil−1; and, residence time, 3 − 12 s. Products have been lumped according to the fractionation made in refineries in: dry gas, liquefied petroleum gases, gasoline, light cycle oil and coke. The results reveal that the co-feeding of any of the naphthas hinders the over-cracking increasing the contents of gasoline and that it inhibits the condensation reactions that produce coke. Two main factors contribute to these results: (i) the competitive adsorption and reaction between the components of the naphthas and the VGO; and (ii) the shortening of the residence time caused by an increase of the flow when the naphtha is co-fed. It should be highlighted the variation in the composition of the gasoline produced with the blends, with overall reductions of the contents of olefins and aromatics.

[EN] An extra-heavy crude oil was treated at a short contact time in the 510-580 degrees C temperature range in a FCC-like process, first thermally and then in the presence of a solid with low catalytic activity. The treatment greatly improved the properties of the crude oil, reducing the density and viscosity to values that make the oil transportable without dilution in a pipeline. In addition, the upgraded oil was substantially free of contaminants such as metals and heptane insolubles. The use of the solid allowed upgrading all properties with a minimum coke penalty. The residual fraction of the upgraded oil had to be eliminated to obtain a syncrude stable in asphaltene proof, which could be obtained by recycling to extinction in a cracking reactor., The authors thank ECOPETROL SA for material and financial support as well as permitting publishing this manuscript. Financial support by the Spanish Government-MINECO through the program "Severo Ochoa" (SEV 2016-0683), CTQ2015-70126-R (MINECO/FEDER), and by the Generalitat Valenciana through the Prometeo program (PROMETEOII/2013/011) is also acknowledged.

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.

Predictive correlations are presented for thermal conversion of petroleum residues employing a large number of data points obtained from the literature. The proposed correlations include equations adopted in terms of three operating variables of temperature, reaction time, and pressure and three main characteristics of a residuum including API, sulfur content, and CCR to predict upgrading conversion, liquid yield, gas yield, sulfur content of the liquid product, and yield of heavy gas oil. The expressions employed in these correlations were carefully chosen from a large group of functions with a minimum number of regression variables. The trends of the dependent variables in terms of the six independent modeling variables are discussed. Satisfactory statistical results were achieved for all correlation models presented, indicating their applicability to different types of residues over a wide range of operating conditions.

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.

The rise in heavy oil reserves, the scarceness of light oils, the demand for clean products and the increase in residual material or bottoms make it necessary to implement or adapt technologies to process heavy oils efficiently. To this end, the modification of the current visbreaking system has been proposed, consisting of adapting a fixed bed inside the reactor in order to study possible modifications in the different thermal processes to increment and improve performance with the purpose of obtaining more valuable products from heavy oils. This research was conducted through testing at the pilot plant level in the visbreaking unit of Ecopetrol S.A. - Instituto Colombiano del Petroleo (ICP), which provides the possibility of comparing the normal visbreaking process to the fixed-bed visbreaking process as a thermal process. Both processes are carried out in comparison to the increase in the performance of middle distillates and the quality properties of the products obtained. The comparison was completed under the same conditions of flow, flow direction (ascending), pressure, temperature and oil type. The results revealed that the fixed-bed visbreaking process managed to convert more heavy fractions into distillates (4 to 7%) compared to the normal visbreaking process.

Catalyst is crucially important to reduce the viscosity of heavy oil during the catalytic aquathermolysis. SO4 2−-modified ZrO2-based nanoparticle catalyst is a commonly used catalyst. But less acid sites and poor hydrothermal stability limited further improving its catalytic performance and practical application. In this study, the Zr-doped silicalite zeolite catalysts with large surface area were prepared as a support matrix, and SO4 2−-modified Zr-doped silicalite zeolite (denoted as SO4 2−/Zr-silicalite-1 zeolite) was used as a solid superacid catalyst to crack the heavy oil. A reference catalyst of SO4 2−/Zr-SiO2 nanoparticles (NPs) was also prepared, which has the same composition with the SO4 2−/Zr-silicalite-1 zeolite catalyst. Compared with the SO4 2−/Zr-SiO2 NP catalyst, the amount of acid sites for the SO4 2−/Zr-silicalite-1 zeolite catalyst is significantly increased and the viscosity reduction efficiency is also enhanced by 40%. More importantly, the SO4 2−/Zr-silicalite-1 zeolite catalyst exhibits a high hydrothermal stability. After catalytic aquathermolysis, the quality of the heavy oil was also ameliorated. The heavy resins and asphaltenes reduced, while the light saturated and aromatic hydrocarbon increased. The results suggest metal element-doped silicalite zeolite catalyst is a potential useful way to solving the less acid sites and poor hydrothermal stability for the SO4 2−-modified nanoparticle catalyst.

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.

Results of a study of the counterflow five-stage extraction of light visbreaker gasoil with N-methylpyrrolidone and phenol are reported. To preclude formation of azeotropes, gasoil was preliminarily separated into light and heavy fractions. Phenol with 10% water was used as a solvent for the light fraction, and N-methylpyrrolidone, for the heavy fraction. It is shown that the raffinates obtained can be used to produce diesel fuel of K-5 ecological class according to the technical regulations of the Customs Union by subsequent hydrotreatment at moderate pressures.

Direct coal liquefaction (DCL) is a process for converting coal to synthetic oils, which can be refined to make transportation fuels. Residue from this process contains inorganic material such as mineral matter originating from the coal and catalysts, and organic matter such as unconverted coal, heavy oils, pre-asphaltenes and asphaltenes. The conversion of these DCL residues to lighter, high-value products is an important step in helping to make this technology both commercially viable and environmentally acceptable. This paper provides an overview of the physico-chemical characteristics and processing options available for coal liquefaction residues and compares and contrasts them to those of petroleum residues. Residue properties vary considerably, since they are highly dependent on feed coal, process configuration and operating conditions. Determination of composition and structural parameters of products derived from residue conversion can help determine their stability, coking and solvent hydrogen donating ability. Thermal conversion processes such as visbreaking and gasification offer the greatest promise for handling these heavy materials. The conversion chemistry, reactivity and kinetics of residue gasification are not well-understood but are important in optimising hydrogen production for the process. The literature has been comprehensively reviewed to provide characteristics and properties of residues and their potential for conversion. In addition, the potential for producing high-value carbon products from residues is briefly discussed.