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Twelve crude oil blends prepared from seven individual crude oils and an imported atmospheric residue were characterized through a true boiling point (TBP) distillation analysis and their density. When comparing the measured TBP fraction yields with those estimated through the application of the additive blending rule, it was found that, for four crude oil blends, the additive blending rule was valid, while for the remaining eight crude oil blends, deviations of the measured TBP yields from the estimated ones were bigger than the TBP analysis’s repeatability limits. By the use of intercriteria analysis evaluation of the data for the deviation of the TBP yields from the additive blending rule and the molar excess volume of the crude oil blends, statistically meaningful relations between the delta TBP yields of light and heavy naphtha, as well as vacuum residue with the molar excess volume, were found. The higher the magnitude of the crude oil blend’s molar excess volume, the bigger the deviations of the TBP yields of naphtha and vacuum residue are. The bigger the deviation of the crude oil blend’s behavior from that of the regular solution, as quantified by the molar excess volume, the bigger the deviations of the TBP yields of naphtha and vacuum residue are.

The production of heavy fuel oil from hydrocracked vacuum residue requires dilution of the residue with cutter stocks to reduce viscosity. The hydrocracked residue obtained from different vacuum residue blends originating from diverse crude oils may have divergent properties and interact with the variant cutter stocks in a dissimilar way leading to changeable values of density, sediment content, and viscosity of the obtained fuel oil. H-Oil hydrocracked vacuum residues (VTBs) obtained from different crude blends (Urals, Siberian Light (LSCO), and Basrah Heavy) were diluted with the high aromatic fluid catalytic cracking (FCC) light cycle, heavy cycle, and slurry oil, and the low aromatic fluid catalytic cracking feed hydrotreater diesel cutter stocks and their densities, sediment content, and viscosity of the mixtures were investigated. Intercriteria analysis evaluation of the data generated in this study was performed. It was found that the densities of the blends H-Oil VTB/cutter stocks deviate from the regular solution behavior because of the presence of attractive and repulsive forces between the molecules of the H-Oil VTB and the cutter stocks. Urals and Basrah Heavy crude oils were found to enhance the attractive forces, while the LSCO increases the repulsive forces between the molecules of H-Oil VTBs and those of the FCC gas oils. The viscosity of the H-Oil VTB obtained during hydrocracking of straight run vacuum residue blend was established to linearly depend on the viscosity of the H-Oil vacuum residue feed blend. The applied equations to predict viscosity of blends containing straight run and hydrocracked vacuum residues and cutter stocks proved their good prediction ability with an average relative absolute deviation (%AAD) of 8.8%. While the viscosity was found possible to predict, the sediment content of the blends H-Oil VTBs/cutter stocks was recalcitrant to forecast.

The exactitude of petroleum fluid molecular weight correlations affects significantly the precision of petroleum engineering calculations and can make process design and trouble-shooting inaccurate. Some of the methods in the literature to predict petroleum fluid molecular weight are used in commercial software process simulators. According to statements made in the literature, the correlations of Lee–Kesler and Twu are the most used in petroleum engineering, and the other methods do not exhibit any significant advantages over the Lee–Kesler and Twu correlations. In order to verify which of the proposed in the literature correlations are the most appropriate for petroleum fluids with molecular weight variation between 70 and 1685 g/mol, 430 data points for boiling point, specific gravity, and molecular weight of petroleum fluids and individual hydrocarbons were extracted from 17 literature sources. Besides the existing correlations in the literature, two different techniques, nonlinear regression and artificial neural network (ANN), were employed to model the molecular weight of the 430 petroleum fluid samples. It was found that the ANN model demonstrated the best accuracy of prediction with a relative standard error (RSE) of 7.2%, followed by the newly developed nonlinear regression correlation with an RSE of 10.9%. The best available molecular weight correlations in the literature were those of API (RSE = 12.4%), Goosens (RSE = 13.9%); and Riazi and Daubert (RSE = 15.2%). The well known molecular weight correlations of Lee–Kesler, and Twu, for the data set of 430 data points, exhibited RSEs of 26.5, and 30.3% respectively.

Forty-eight crude oils with variations in specific gravity (0.782 ≤ SG ≤ 1.002), sulphur content (0.03 ≤ S ≤ 5.6 wt.%), saturate content (23.5 ≤ Sat. ≤ 92.9 wt.%), asphaltene content (0.1 ≤ As ≤ 22.2 wt.%), and vacuum residue content (1.4 ≤ VR ≤ 60.7 wt.%) were characterized with HTSD, TBP, and SARA analyses. A modified SARA analysis of petroleum that allows for the attainment of a mass balance ≥97 wt.% for light crude oils was proposed, a procedure for the simulation of petroleum TBP curves from HTSD data using nonlinear regression and Riazi’s distribution model was developed, and a new correlation to predict petroleum saturate content from specific gravity and pour point with an average absolute deviation of 2.5 wt.%, maximum absolute deviation of 6.6 wt.%, and bias of 0.01 wt.% was developed. Intercriteria analysis was employed to evaluate the presence of statistically meaningful relations between the different petroleum properties and to evaluate the extent of similarity between the studied petroleum crudes. It was found that the extent of similarity between the crude oils based on HTSD analysis data could be discerned from data on the Kw characterization factor of narrow crude oil fractions. The results from this study showed that contrary to the generally accepted concept of the constant Kw characterization factor, the Kw factors of narrow fractions differ from that of crude oil. Moreover, the distributions of Kw factors of the different crudes were different.

Ten gas oils and one deasphalted hydrocracked vacuum residue obtained from ebullated-bed vacuum residue hydrocracking have been cracked in a laboratory advanced catalyst evaluation unit on a commercial fluid catalytic cracking (FCC) catalyst. It was found that the eleven secondary heavy oils obey second-order reaction kinetics. The relations between gas oil properties and FCC conversion, product yields, and quality were evaluated by means of intercriteria analysis. It could be stated that the FCC conversion strongly correlates with the gas oil Kw characterization factor. The product yields were established to depend on the secondary gas oil carbon atoms number, aromatic ring index, paraffinic and aromatic carbon content, and the total aromatics content.

Four straight run vacuum residual oils (SRVRO) and five H-Oil hydrocracked vacuum residual oils (H-Oil VTB) and their blends were oxidized in a laboratory autoclave reactor. It was found that the a...

The intercriteria analysis developed on the base of intuitionistic fuzziness and index matrices was applied to evaluate processing data of the LUKOIL Neftohim Burgas H-Oil ebullated bed vacuum residue hydrocracker with the aim of revealing the reasons for increased fouling registered during the 3rd cycle of the H-Oil hydrocracker. It was found that when the ratio of the ΔT of the 1st reactor to the ΔT of the 2nd reactor gets lower than 2.0, an excessive H-Oil equipment fouling occurs. The fouling was also found to be favored by processing of lower Conradson carbon content vacuum residual oils and increased throughput and depressed by increasing the dosage of the HCAT nanodispersed catalyst. The fouling in the atmospheric tower bottom section is facilitated by a lower aromatic content in the atmospheric tower bottom product. The addition of FCC slurry oil not only increases aromatic content but also dissolves some of the asphaltenes in the atmospheric residual hydrocracked oil and decreases its colloidal instability index. The fouling in the vacuum tower bottom section is facilitated by a higher saturate content in the VTB. Surprisingly, it was found that the asphaltene content in the VTB depresses the fouling rate. No relation was found of the sediment content in the hydrocracked residual oils measured by hot filtration tests and by the centrifuge method to the equipment fouling of the H-Oil hydrocracker.

The performance of both ebullated bed H-Oil vacuum residue (VR) hydrocracking and fluid catalytic cracking (FCC) of vacuum gas oils (VGO) is interrelated. The increase of H-Oil unit reaction temper...

Model compounds were used to provide some chemical boundaries for the eight-fraction SAR-ADTM characterization method for heavy oils. It was found that the Saturates fraction consists of linear and highly cyclic alkanes; the Aro-1 fraction consists of molecules with a single aromatic ring; the Aro-2 fraction consists of mostly 2 and 3-ring fused aromatic molecules, the pericondensed 4-ring molecule pyrene, and molecules with 3–5 rings that are not fused; and the Aro-3 fraction consists of 4-membered linear and catacondensed aromatics, larger pericondensed aromatics, and large polycyclic aromatic hydrocarbons. The Resins fraction consists of mostly fused aromatic ring systems containing polar functional groups and metallated polar vanadium oxide porphyrin compounds, and the Asphaltene fraction consists of both island- and archipelago-type structures with a broad range of molecular weight variation, aromaticity, and heteroatom contents. The behavior of the eight SAR-ADTM fractions during hydrocracking and pyrolysis was investigated, and quantitative relations were established. Intercriteria analysis and evaluation of SAR-ADTM data of hydrocracked vacuum residue and sediment formation rate in commercial ebullated bed vacuum residue hydrocracking were performed. It showed that total asphaltene content, toluene-soluble asphaltenes, and colloidal instability index contribute to sediment formation, while Resins and Cyclohexane-soluble asphaltenes had no statistically meaningful relation to sediment formation for the studied range of operation conditions.

Four nonlinear regression techniques were explored to model gas oil viscosity on the base of Walther’s empirical equation. With the initial database of 41 primary and secondary vacuum gas oils, four models were developed with a comparable accuracy of viscosity calculation. The Akaike information criterion and Bayesian information criterion selected the least square relative errors (LSRE) model as the best one. The sensitivity analysis with respect to the given data also revealed that the LSRE model is the most stable one with the lowest values of standard deviations of derivatives. Verification of the gas oil viscosity prediction ability was carried out with another set of 43 gas oils showing remarkably better accuracy with the LSRE model. The LSRE was also found to predict better viscosity for the 43 test gas oils relative to the Aboul Seoud and Moharam model and the Kotzakoulakis and George.

This study highlights the importance of the condition of the catalytic system in the ebullated bed vacuum residue hydrocracker on the performance of the unit, proving that not only feedstock qualit...

Thirty crude oils, belonging to light, medium, heavy, and extra heavy, light sulfur, and high sulfur have been characterized and compatibility indices defined. Nine crude oil compatibility indices have been employed to evaluate the compatibility of crude blends from the thirty individual crude oils. Intercriteria analysis revealed the relations between the different compatibility indices, and the different petroleum properties. Tetra-plot was employed to model crude blend compatibility. The ratio of solubility blending number to insolubility number was found to best describe the desalting efficiency, and therefore could be considered as the compatible index that best models the crude oil blend compatibility. Density of crude oil and the n-heptane dilution test seem to be sufficient to model, and predict the compatibility of crude blends.

Inter-criteria analysis was employed in VGO samples having a saturate content between 0.8 and 93.1 wt.% to define the statistically significant relations between physicochemical properties, empirical structural models and vacuum gas oil compositional information. The use of a logistic function and employment of a non-linear least squares method along with the aromatic ring index allowed for our newly developed correlation to accurately predict the saturate content of VGOs. The empirical models developed in this study can be used not only for obtaining the valuable structural information necessary to predict the behavior of VGOs in the conversion processes but can also be utilized to detect incorrectly performed SARA analyses. This work confirms the possibility of predicting the contents of VGO compounds from physicochemical properties and empirical models.

Three H-Oil gas oils, heavy atmospheric gas oil (HAGO), light vacuum gas oil (LVGO), heavy vacuum gas oil (HVGO), and two their blends with hydrotreated straight run vacuum gas oils (HTSRVGOs) were cracked on two high unit cell size (UCS) lower porosity commercial catalysts and two low UCS higher porosity commercial catalysts. The cracking experiments were performed in an advanced cracking evaluation fluid catalytic cracking (FCC) laboratory unit at 527 °C, 30 s catalyst time on stream, and catalyst-to-oil (CTO) variation between 3.5 and 7.5 wt/wt The two high UCS lower porosity catalysts were more active and more coke selective. However, the difference between conversion of the more active high UCS lower porosity and low UCS higher porosity catalysts at 7.5 wt/wt CTO decreased in the order 10% (HAGO) > 9% (LVGO) > 6% (HVGO) > 4% (80% HTSRVGO/20% H-Oil VGO). Therefore, the catalyst performance is feedstock-dependent. The four studied catalysts along with a blend of one of them with 2% ZSM-5 were examined in a commercially revamped UOP FCC VSS unit. The lower UCS higher porosity catalysts exhibited operation at a higher CTO ratio achieving a similar conversion level with more active higher UCS lower porosity catalysts. However, the higher UCS lower porosity catalysts made 0.67% Δ coke that was higher than the maximum acceptable limit of 0.64% for this particular commercial FCC unit (FCCU), which required excluding the HVGO from the FCC feed blend. The catalyst system containing ZSM-5 increased the LPG yield but did not have an impact on gasoline octane. It was found that the predominant factor that controls refinery profitability related to the FCCU performance is the FCC slurry oil (bottoms) yield.

The gasoline blending prediction models available in the open literature: Linear method, Ethyl method, Stewart method, Zahed method, and Twu method were tested on 25 gasoline blends prepared from 14 components used by LUKOIL Neftohim Burgas (LNB) refinery to produce commercial gasoline grades. The performed tests with these models showed prediction accuracy outside of the acceptable ASTM D 2699 and ASTM D 2700 reproducibility limits. However, the LNB-modified regression model of Zahed method turned out to predict RON and MON of studied gasoline blends with accuracy equivalent to the reproducibility of the standard methods for measurement of RON and MON.

This paper passes over the literature for residual oil characterization. The methods for residual oil characterization are classified in: characterization based on physical and chemical bulk properties; characterization based on saturates, aromatics, resins, asphaltenes (SARA) analysis; and characterization based on the molecular modeling processes. The upper and lower limits of the values for physical and chemical bulk properties of the vacuum residual oils around the world are outlined. A variation of the physical and chemical bulk properties of SARA fractions originating from different vacuum residual oils is discussed. Correlations between refractive index and density, and between the vapor pressure osmometry (VPO) molecular weight of saturates and aromatics were found. A ratio between the lowest and the highest molecular weight of the vacuum residual oil saturate and aromatic fraction of 2.4 was found showing that the molecular weights of these SARA fractions are not fixed and can vary between 360 and 880 g/mole for the saturates, and 450 and 1080 g/mole for the aromatics. Assuming the same ratio in variation of molecular weights (MW) of the fractions resins and asphaltenes for the reviewed 41 vacuum residual oils suggests that the resins MW could vary in the range 800 ÷ 1800 g/mole and the asphaltenes MW may vary between 1000 and 3000 g/mole. The application of sophisticated analytical techniques showed a very big diversity in the species building the vacuum residual oils and different distribution of these species even for the same SARA fraction depending on the residual oil origin. The different approaches for “molecular reconstruction” of residual oils Monte Carlo (MC), Quadrature algorithm (QA), Entropy maximization (EM), quantitative structure-property relationship (QSPR), structure-oriented lumping (SOL), molecular type homologous series (MTHS) matrix, artificial neural network (ANN) and multiple linear regression (MLR) are reviewed. A conclusion is made that the advanced analytical and computational techniques are still an obligor to the chemical engineers working at the commercial residual oil conversion units who aim to optimize the conversion process performance.

This work presents characterization data and viscosity of 34 secondary vacuum gas oils (H-Oil gas oils, visbreaker gas oils, and fluid catalytic cracking slurry oils) with aromatic content reaching up to 100 wt.%. Inter-criteria analysis was employed to define the secondary VGO characteristic parameters which have an effect on viscosity. Seven published empirical models to predict viscosity of the secondary vacuum gas oils were examined for their prediction ability. The empirical model of Aboul-Seud and Moharam was found to have the lowest error of prediction. A modification of Aboul-Seoud and Moharam model by separating the power terms accounting for the effects of specific gravity and average boiling point improves the accuracy of viscosity prediction. It was discovered that the relation of slope of viscosity decrease with temperature enhancement for the secondary vacuum gas oil is not a constant. This slope increases with the average boiling point and the specific gravity augmentation, a fact that has not been discussed before.

This paper evaluates the influence of crude oil (vacuum residue) properties, the processing of fluid catalytic cracking slurry oil, and recycle of hydrocracked vacuum residue diluted with fluid catalytic cracking heavy cycle oil, and the operating conditions of the H-Oil vacuum residue hydrocracking on the quality of the H-Oil liquid products. 36 cases of operation of a commercial H-Oil® ebullated bed hydrocracker were studied at different feed composition, and different operating conditions. Intercriteria analysis was employed to define the statistically meaningful relations between 135 parameters including operating conditions, feed and products characteristics. Correlations and regression equations which related the H-Oil® mixed feed quality and the operating conditions (reaction temperature, and reaction time (throughput)) to the liquid H-Oil® products quality were developed. The developed equations can be used to find the optimal performance of the whole refinery considering that the H-Oil liquid products are part of the feed for the units: fluid catalytic cracking, hydrotreating, road pavement bitumen, and blending.

H-Oil vacuum gas oils obtained during hydrocracking of vacuum residual oils originated from the crudes Russian Export Blend, Basrah light, and Heavy Kazakh were cracked in a mixture with a hydrotreated vacuum gas oil in the LUKOIL Neftohim Burgas commercial fluid catalytic cracking (FCC) unit. Some of the H-Oil vacuum gas oils were also cracked in a laboratory FCC (ACE) unit. The results from the commercial and the laboratory tests showed that the laboratory FCC experiments in an ACE unit can be used to evaluate the effect of feed quality on the commercial FCC unit performance. The assumption that the conversion of a vacuum gas oil (VGO) blend in the fluid catalytic cracking could be considered as a linear combination of the conversion of the individual components made by other researchers was also confirmed in this study. The higher the hydrogen content in the vacuum residual oil of a crude is the higher the FCC conversion of the H-Oil VGO, obtained during hydrocracking of that high saturate vacuum residual oil, will be expected.

This work summarizes the results of multiple experiments performed in the LUKOIL Neftohim Burgas Research Laboratory related to the issue of high values of hot filtration test (HFT) of the residue H-Oil hydrocracking residual oil products. After the start-up of the new residue H-Oil hydrocracker in the LUKOIL Neftohim Burgas refinery during the second half of 2015 the values of the HFT of the vacuum tower bottom product varied between 0.01 and 8.7%. It was found that the vacuum residual oil feed source has a profound effect on the processes of sedimentation in the H-Oil hydrocracker. The processing of vacuum residual oils from Arab medium, Arab heavy, and Basrah light crudes reduced the sedimentation and allowed achievement of a higher conversion. The H/C ratios of asphaltenes from all studied feeds decreased after hydrocracking. However, the decrease of the H/C ratio was the least pronounced with the Basra light asphaltenes, while the H/C ratios of asphaltenes from the vacuum residual oils originating fr...

Data from assays of 244 crude oils (condensates, extra light, light, intermediate, and heavy crudes) were processed by the InterCriteria Analysis with the aim to investigate the relationships between bulk properties and fraction properties of the crude oils and the degree of similarity between them. It was found that except the crude bulk properties sulfur, Conradson carbon, and metals content all other studied crude bulk properties exhibited lack of statistically meaningful relations or presence of weak statistically meaningful relations with the crude fraction properties. The use of the InterCriteria Analysis showed that crudes with very similar properties could be identified when a large crude database is available. In this way based on a previous experience in oil refining a selection of potentially beneficial new crudes for processing in a refinery could be made.

Five empirical methods toestimate the content of aromatic, naphthenic, and paraffinic carbon and hydrogen content and the bulk properties were tested for prediction of aromatic structures content of 95 vacuum gas oils. The density demonstrated the highest correlation with the aromatic structures content among all other studied bulk properties and empirical parameters. The aromatic structures content could be predicted by a second order power law dependence on density with accuracy commensurable with the reproducibility of SARA analysis. The poly-nuclear aromatic structures content was also found to depend on the density and can be expressed by a linear function.

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.

Sixteen petroleum crudes and an imported atmospheric residue originating from Russia, Azerbaijan, Greece, Italy, Kuwait, Iraq, Iran, Saudi Arabia, Tunisia, and the USA have been processed in the LUKOIL Neftohim Burgas (LNB) refinery, and their effect on the ebullated bed vacuum residue H-Oil hydrocracking (EBVRHC) performance has been evaluated. The vacuum residue conversion in the LNB H-Oil EBVRHC varied between 55% and 82% depending on the crude blend processed in the LNB refinery. It has been established that among all vacuum residue SARA fractions during EBVRHC, the resins have the highest conversion, followed by the naphtheno-aromatics while the saturates show the lowest conversion. Depending on the petroleum crude origin the behaviour of the most problematic VR asphaltene fraction has been found to be different suggesting distinct propensity of the asphaltenes from the different petroleum crudes to participate in radical recombination reactions leading to the formation of additional amounts of core-condensed asphaltenes.

A rapid and simple method for the determination of benzene and oxygenates in petroleum by heart-cutting gas chromatography is reported. Experimental design was used to optimize the chromatographic resolution with a short analysis time by improving the injection volume, split ratio, oven temperature, and oven ramps, with seven Deans’ switching heart-cutting applications. The analyses were performed by internal standardization and seven oxygenates and benzene were determined within 20 min. The calibration curves were linear across the tested ranges. The developed method was validated; the precision and accuracy were lower than 2.0 and 2.8%, respectively. The uncertainty was between ±0.012 and ±0.04%.

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.

Kinetic data for hydroperoxide formation in a commercial biodiesel, produced from 50% sunflower oil and 50% rapeseed oil were obtained by using rapid, higher than standard temperature procedure with sufficient oxygen solubility in the samples. Three different mathematical methods for processing the data and shelf life determination of the studied biodiesel are compared. The applicable methodologies are hydroperoxide concentration abrupt increase graphical determination and Q rule. The calculation shows that shelf life of the studied stabilized Bulgarian biodiesel amounts between 1.17 and 1.27 years. It was also found that peroxide value for induction period at 15 °C is 71.8 meq O 2 /kg biodiesel.

The thermal conversion of fifteen vacuum residual oils (VROs) having different properties was investigated in a modified high-temperature–high-pressure batch autoclave reactor. It was found that the sediment level (toluene insoluble) in the unconverted residual oil demonstrated a behavior typical for presence of induction period. The sediment level at the end of the induction period was mostly influenced by feedstock colloidal stability. The rate of sediment formation after the induction period was mostly influenced by VRO resin content. The results in this study do not support the assumption that the more aromatic VROs generate more coke-like sediments during thermal conversion. The higher density and aromatic VROs generated less sediment. The addition of high aromatic fluid catalytic cracking (FCC) slurry oil to a VRO decreased the thermal reactor surface deposit. The effect of this coke-like reactor sediment reduction is attributed to improvement in VRO asphaltene solubility by the high aromatic FCC slurry oil and a possible hydrogen donating properties of this gas oil. The use of a synthetic dispersant was found to improve the asphaltene solubility limit and extend the period of conversion without forming coke-like deposit in the thermal cracking reactor. The FCC slurry demonstrated a stronger inhibition effect on sediment formation than the synthetic dispersant probably because it is a stronger solvent and/or because it possesses hydrogen donating properties.

Lukoil Neftohim Burgas (LNB), the single refinery currently operating in Bulgaria, constructed and put into operation a new high pressure diesel hydrotreater in 2010. Since its start-up, the unit has operated smoothly by hydrotreating a heavy diesel fraction (200–360 °C) with sulfur content of 0.8% and density at 20 °C of 0.860 g/cm 3 and producing hydrotreated diesel with sulfur content of 6 ppm and density at 20 °C of 0.847 g/cm 3 . However, in 2013 a sudden increase of the pressure of the treating gas compressor at the hydrotreater scheme was registered and the unit had to be switched off in emergency. Sediments formed in the tubes of the heat-exchanger, used for heat transfer between the hydrotreater product and hydrogen treating gases, were found. This study presents the results from the determination of the composition and the origin of the deposit, as well as the technological solutions to prevent its formation. According of the data from different analytical techniques applied, the following composition of the deposit was supposed: 46.6% ammonium chloride, 9.6% nitrates, 13.6% organic chlorides and about 30% water, organic impurities (carbonic acids and naphthenic hydrocarbons) and corrosion products. Numerical investigation of the temperature field in the area of the deposits is also presented.

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.

Evaluation of opportunity to raise Euro V diesel production by increasing fluid catalytic cracking (FCC) light cycle oil (LCO) production was carried at the Lukoil Neftochim Bourgas, Bulgaria (LNB) refinery. The FCC LCO (IBP-360 °C) production was investigated in the FCC conversion range between 69 and 83 wt.% and LCO initial boiling point (IBP) between 177 and 210 °C. It was found that the LCO yield increased from 16.0 up to 20.7 wt.% by decreasing conversion from 83 to 69 wt.%. At constant conversion in the FCC unit of 79.7 wt.% the LCO yield increased from 17.8 to 24.8 wt.% by decreasing the IBP from 210 to 177 °C. A further 3.5 wt.% LCO yield increase and meeting the diesel flash point specification of 55 °C can be achieved by lowering the LCO IBP down to 163 °C. It was found that during hydrotreatment of a blend of the LNB middle distillates and LCO in a high pressure (70 bars) hydrotreater employing Co-Mo catalyst the maximum LCO (IBP = 210; FBP = 300 °C) content that allows meeting the EN specifications is 10 wt.%. If the LCO IBP is reduced to 177 °C then the maximum LCO content in the feed can reach 20 wt.%. The limitation of density not higher than 0.845 g/cm3 in the hydrotreated product at 15 °C is the restriction for further increase of LCO content in hydrotreater feed. Replacing the Co-Mo catalyst by Ni-Mo and noble metal catalysts in the high pressure hydrotreater can allow more than double increase of LCO content in hydrotreater feed. Hydrogen chemical consumption in that case, however is also more than twofold.

Cold flow properties and oxidation stability of near zero sulfur diesel from Ural crude oil and fatty methyl esters (FAME) from different origin and their blends were studied in this work. It was found that undercutting the petroleum diesel to obtain arctic diesel deteriorates its oxidation stability and anti-oxidant addition is required to keep the oxidation stability within acceptable limits. The addition of commercially available FAMEs, produced from 100% rape seed oil; 70% soya and 30% palm oil; 50% rape seed oil and 50% sunflower oil, to the petroleum diesel depresses the cold filter plugging point (CFPP). The depressing effect on the conventional diesel CFPP of the FAME depends on the petroleum diesel and the FAME properties. The Honeywell software RPMS model used to predict cloud points (CP) of blends of different conventional middle distillates was found to be capable of predicting cloud points of blends of petroleum diesel and FAME. The highest class 4 of arctic diesel according to EN 590 (CP = −34 °C; CFPP = −44 °C) can be produced by blending petroleum diesel with the 100% rape seed FAME treated with cold flow improver in concentration up to 10%. The addition of the synthetic anti-oxidant ionol (BHT) to petroleum diesel with high unsaturated hydrocarbon level and to the blends petroleum diesel/FAME seems to inhibit the secondary reactions of peroxides decomposition to acids to a greater extent than the oxidative polymerization.

This paper investigates the effect of fluid catalytic cracking (FCC) feed hydrotreatment and its severity increase on product yields and quality obtained in a commercial and a laboratory MAT FCC units. The hydrotreatment of Ural heavy vacuum gas oil reduces not only sulfur, nitrogen, Conradson carbon and metals content in the FCC feed but also increases the mononuclear aromatic hydrocarbons content by 8% absolute at almost no change in the total aromatics content. Regardless of this 8% increase of the mononuclear aromatics in the hydrotreated FCC feed the conversion increase in both commercial and laboratory MAT units was only 2%. The severity increase in the FCC feed hydrotreater leads to a higher conversion in the FCC, higher hydrogen transfer rate that results in higher isobutane/butylenes ratio, lower gasoline olefins content, and higher gasoline motor octane number. The hydrotreatment of the Ural heavy vacuum gas oil exhibited the same changes in FCC catalyst selectivities: lower coke and LCO selectivities and higher gasoline selectivity in both commercial riser FCC unit that has between 2 and 3 s time on stream, and the fixed bed reactor MAT unit, that has 30 s time on stream.

Hydrotreated vacuum gasoil from straight-run distillation of a Russian export mixture (GRES) and the same gasoil after treatment with sulfuric acid (OGRES) so that nitrogen-containing compounds were totally removed and the hydrocarbon composition was almost unchanged were investigated as catalytic feedstock. Cracking was conducted on a MAT laboratory setup with different catalyst and feedstock ratios, constant reactor temperature of 527°C, and feedstock contact time with catalyst of 30 sec. Elimination of nitrogen-containing compounds from GRES increased the yield of cyclic hydrocarbons in the naphtha cut with lower aromatization and decreased the yield of macromolecular aliphatic hydrocarbons with lower olefination. In the absence of basic nitrogen, the activity and selectivity of the catalyst for the naphtha and light cyclic petroleum products increased. The naphtha obtained from OGRES, in comparison to the naphtha obtained from GRES, contains more cycloalkanes and less alkanes and alkenes and has lower research and motor octane numbers.

Six H-Oil-based residual fuel oils, two H-Oil atmospheric tower bottom products, two H-Oil vacuum tower bottom products, one visbreaker-based residual fuel oil, and three different straight run vacuum residual oils were studied in this work. The colloidal stability parameters S-value (ASTM D7157), and separability number (ASTM D7061), along with SARA-based colloidal instability index, and the solubility parameters of asphaltene and maltene fractions of the studied residual oils were tested to correlate with the residual oil sediment content. It was found that none of the colloidal stability parameters correlated with the residual oil sediment content, while correlations were found between the different colloidal stability parameters. This study has shown that only the residual oil samples whose S-value has been at minimum of 1.375 kept their sediment contents without change with the course of time. [Received: August 1, 2016; Accepted: December 4, 2016]

This study focuses on investigating the conversion behaviour of vacuum residue and blends with heavy VGO (480-540°C) and atmospheric residue (340°C+), three fractions originating from the same Russian export blend crude oil (REBCO), in a laboratory ebullated bed hydrocracking pilot plant unit and in the LUKOIL Neftohim Burgas commercial H-OilRC hydrocracker. It was found that the vacuum residue conversion was 1.7 times as high as that of the VGO at the same operating conditions in both laboratory and in the commercial H-OilRC hydrocracking unit. No increase in the sediment content of the atmospheric residue product, obtained during hydrocracking of the lighter feeds, was observed. It was found that the vacuum residue H-Oil hydrocracking is best described by 1.5 order kinetics. This study showed that co-processing of distillate material (mainly vacuum gas oil) is an option to increase capacity of an existing H-OilRC residue hydrocracker while also improving the VGO product quality without adversely impacting sediment levels in the unconverted residue product. [Received: February 2, 2017; Accepted: September 21, 2017]

Industrial experiments on the addition of H2S to the fluid catalytic cracking (FCC) feed (hydrotreated vacuum gas oil) were carried out in the commercial FCC unit at Lukoil Neftochim, Bulgaria. It was found that during cracking of pure hydrotreated vacuum gas oil to which was added about 550 ppm H2S that the FCC gasoline contained about 12 ppm more sulfur than the nonspiked feed. Both gasolines obtained from the pure feed and the H2S-spiked feed contained the same type of sulfur compounds: mercaptans, thiophenes, and benzothiophenes. In the case of the H2S-spiked feed, the additional FCC gasoline sulfur formed was about 1.2% of the sulfur in the H2S added to the feed. The FCC gasoline sulfur formed from the pure FCC feed, on the other hand, was about 2.5% of the sulfur in the feed. The higher percent of sulfur conversion of the pure FCC feed relative to the conversion of the H2S suggests that both reaction of H2S with olefins or diolefins (from the catalytic cracking of the hydrocarbons of the feed) and t...