Heavy Petroleum Fractions Research Articles

A dynamic non-isothermal model for a hydrocracking reactor: Model development by the method of continuous lumping and application to an industrial unit

Hydrocracking is an important refinery process which is carried out in catalytic reactors to convert heavy petroleum fractions into valuable products. Because of the large number of species and complex reactions involved, modeling of hydrocracking is a challenging task. In this paper a dynamic, non-isothermal reactor model has been constructed using the method of continuous lumping which treats the complex reactive mixture as a continuum. In doing so concentrations are characterized in terms of reactivity which is a monotonic function of the true boiling point of the mixture. The material and energy balances are developed in the form of integro-differential equations. The significant modeling parameters are identified and estimated using data from an industrial reactor. Steady-state and dynamic predictions of the model outputs such as reactor temperature, product yields and hydrogen consumption are shown to be in good agreement with plant data.

A Review on Carbon-rich Molecules in Space

AbstractWe present and discuss carbon-rich compounds of astrochemical interest such as polyynes, acetylenic carbon chains and the related derivative known as monocyanopolyynes and dicyanopolyynes. Fullerenes are now known to be abundant in space, while fulleranes - the hydrogenated fullerenes - and other carbon-rich compounds such as very large polycyclic aromatic hydrocarbons (PAHs) and heavy petroleum fractions are suspected to be present in space. We review the synthesis, the infrared spectra as well as the electronic absorption spectra of these four classes of carbon-rich molecules. The existence or possible existence in space of the latter molecules is reported and discussed.

Application to SFC-GC × GC to heavy petroleum fractions analysis

The new multidimensional chromatographic instrument SFC-GC×GC enables the temporary storage of SFC fractions inside sampling loops for subsequent analyses by GC×GC. The interface was configured for the characterization of heavy petroleum fractions. The SFC dimension was adapted to perform a group type separation into saturated, unsaturated and polar fractions. The GC×GC dimension was set in order to realize high temperature separations with two sets of columns. In a heart-cutting approach, an extended quantitative characterization of hydrocarbons contained in vacuum gas oil (VGO) was performed in a single run. Subsequently, in a comprehensive approach, quantitative 3D contour plots were built for the same VGO sample. The described application of the SFC-×2GC×GC instrument represents an innovative, rapid and automatic way for obtaining extended quantitative characterizations of heavy petroleum fractions.

Reliability–Based Optimization using Surface Response Methodology to Split Heavy Petroleum Fractions by Centrifugal Molecular Distillation Process

The present work aimed to develop an experimental and computational study for optimizing the centrifugal molecular distillation process to split heavy petroleum fractions. On the basis of the balance equations and Langmuir–Knudsen equation, a mathematical model was proposed. The influence of the evaporator temperature (EVT), the feed flow rate (Q) and the interactions between them, on the overall distillate mass flow rate (D) and the distillate yield (%D) was analyzed. A full 22 factorial central plus star rotatable (α = ±√2) composite design was performed in the experimental range from 423.15 to 603.15 K for EVT and from 1.473 to 4.418 kg · h−1 for Q. The optimized conditions, using response surface methodology, established that the EVT must range from 540 to 600 K and the Q from 1.5 to 3.5 kg · h−1. The comparison of the experiment results with the predicted model results shows an acceptable qualitative agreement between the experiment and simulated data.

Laser-Induced Acoustic Desorption Mass Spectrometry

Large thermally labile molecules were not amenable to mass spectrometric analysis until the development of atmospheric pressure evaporation/ionization methods, such as electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), since attempts to evaporate these molecules by heating induces degradation of the sample. While ESI and MALDI are relatively soft desorption/ionization techniques, they are both limited to preferential ionization of acidic and basic analytes. This limitation has been the driving force for the development of other soft desorption/ionization techniques. One such method employs laser-induced acoustic desorption (LIAD) to evaporate neutral sample molecules into mass spectrometers. LIAD utilizes acoustic waves generated by a laser pulse in a thin metal foil. The acoustic waves travel through the foil and cause desorption of neutral molecules that have been deposited on the opposite side of the foil. One of the advantages of LIAD is that it desorbs low-energy molecules that can be ionized by a variety of methods, thus allowing the analysis of large molecules that are not amenable to ESI and MALDI. This review covers the generation of acoustic waves in foils via a laser pulse, the parameters affecting the generation of acoustic waves, possible mechanisms for desorption of neutral molecules, as well as the various uses of LIAD by mass spectrometrists. The conditions used to generate acoustic or stress waves in solid materials consist of three regimes: thermal, ablative, and constrained. Each regime is discussed, in addition to the mechanisms that lead to the ablation of the metal from the foil and generation of acoustic waves for two of the regimes. Previously proposed desorption mechanisms for LIAD are presented along with the flaws associated with some of them. Various experimental parameters, such as the exact characteristics of the laser pulse and foil used, are discussed. The internal and kinetic energy of the neutral desorbed molecules are also considered. Our research group has been instrumental in the development and use of LIAD. For example, we have systematically examined the influence of many parameters, such as the type of the foil and its thickness, as well as the analyte layer's thickness, on the efficiency of desorption of neutral molecules. The coupling of LIAD with different instruments and ionization techniques allows for broad use of LIAD in our research laboratories. The most important applications involve analytes that cannot be analyzed by using other mass spectrometric methods, such as large saturated hydrocarbons and heavy hydrocarbon fractions of petroleum. We also use LIAD to characterize lipids, peptides, and oligonucleotides. Fundamental research on the reactions of charged mono-, bi-, and polyradicals with biopolymers, especially oligonucleotides, also requires the use of LIAD, as well as thermochemical measurements for neutral biopolymers. These are but a few of the uses of LIAD in our research group.

Complementarity of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and high temperature comprehensive two-dimensional gas chromatography for the characterization of resin fractions from vacuum gas oils

The study focuses on the analytical characterization of resin fractions from vacuum gas oils (VGO) obtained by LC fractionation. These complex matrices are often considered as containing polar compounds, but are rather defined by their physico-chemical properties than by their chemical structures. Therefore resin fractions remain almost unknown. Owing to the energetic context, which imposes to convert heavy petroleum fractions into transportation fuels, they become key matrices to study. Therefore, to obtain detailed structural information, high resolutive analytical techniques have been implemented: high temperature comprehensive two-dimensional gas chromatography (HT-2D-GC) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR/MS). This study provides a unique opportunity to compare these two techniques. Finally innovative compilation of data enables to access unprecedented quantitative extended distributions by carbon atoms number and chemical families on VGO resin fractions. These results are a real progress for the implementation of conversion processes, and open up new prospects for their optimization via kinetic modeling.

Overcoming the high-temperature two-dimensional gas chromatography limits to elute heavy compounds

Overcoming high-temperature (HT) two-dimensional gas chromatography (GC×GC) limits is critical for the analysis of heavy hydrocarbons, particularly those contained in heavy petroleum fractions. To reach this goal, HT-GC×GC analysis was adapted from HT-GC Simulated Distillation (HT-GC SimDist) operating conditions as this analysis embraces compounds whose boiling point ranges from 35°C to 700°C and from a previous study that enabled the elution of linear alkane nC60 and tetraaromatic compounds by HT-GC×GC. This paper shows that HT-GC×GC analysis using CO2 cryogenic modulator and short wide bore columns with a thin film of stationary phase allows the elution of linear alkanes up to nC68 (641°C) as well as of highly aromatic hydrocarbons like coronene. Furthermore, compared to previous studies, an on-column injector was used to reduce discrimination of high boiling point compounds.

Extension of the TBP Curve of Petroleum Using the Correlation DESTMOL

Abstract The properties of natural petroleum and petroleum products make use of the True Boiling Point (TBP) distillation analysis and it has been proved to be very useful for petroleum characterization and design and operation of refinery units. So, the TBP distillation analysis has contributed to the petroleum science and technology, to the classification of petroleum, to the development of petroleum property correlations and it has been used worldwide. However, when applied to heavy petroleum fractions, difficulties are often encountered. Through petroleum distillation curve (TBP), it is possible to evaluate the yields of the products that will be obtained in the refineries, as well as to establish operational strategies and process optimizations, as the cracking process. The TBP curve is very important for the oil industry and is used to understand the behavior of oil before distillation. For when the oil is subjected to a distillation tower on an industrial scale is already known about the percentage of distillate obtained working at a specific temperature. In the oil refining industry as the distillations follow: Atmospheric Distillation (distillation up to 673 K - ASTM D 2892) and vacuum distillation (distillation to 838K - ASTM D 5236). This work creates the possibility of extending the temperature range of distillation of oil to 973K. The goal of this work is extend the TBP by DESTMOL, the extension of the TBP curve oil reaching approximately 973 K exceeding the curves generated so far that reach only 838 K. The DESTMOL correlation applies pretty good showing continuity and asymptotic profile of the TBP curve. The results help to meet the waste oil and can thus use the waste for more noble ends. As the result of DESTMOL, we can better define the strategiesand operating conditions for oil processing, achieving better economic results in the use of heavy oil, due to its better characterization.

Computational Approach for Studying the Laser Radiation Thermal Cracking Process of Heavy Petroleum Fraction: Optimization of Laser Operational Conditions

The temperature distribution related to the radiation thermal cracking process of a heavy petroleum fraction was identified by simulations using ANSYS 12.1 software. To determine the best laser parameters (laser power beam and scanning speed), a set of mathematical models (maximum and minimum temperature, time) was developed from a full 2 factorial design. Laser power beam and scanning speed in the range of 28-32 W and 1.8-2.2 m/s, respectively, were identified as the best set of radiation thermal cracking process parameters.

Regular Solution Theories Are Not Appropriate for Model Compounds for Petroleum Asphaltenes

The solubility, melting point temperature, and enthalpy of fusion of a series of model compounds for heavy petroleum fractions were measured experimentally in n-heptane, toluene, dichloromethane, and mixtures thereof. Two porphyrins (meso-tetraphenylporphyrin and octaethylporphyrin), the vanadyl analogues of the same two porphyrins, and one model asphaltene (4,4′-bis-(2-pyren-1-yl-ethyl)-[2,2′]bipyridinyl) were selected to test the efficacy of the regular solution and the Flory−Huggins theories in predicting the solubility behavior of these complex polyaromatic molecules in organic solvents. These simple solubility models were not capable of qualitatively or quantitatively describing the solubility behavior of these high-melting solid compounds, even with the solubility parameter as an adjustable parameter. Various different methods of estimating the differential heat capacity, ΔCP, improved the fits in certain cases, although no universally acceptable method was identified. Several group contribution the...

Challenge in the speciation of nitrogen-containing compounds in heavy petroleum fractions by high temperature comprehensive two-dimensional gas chromatography

Extending the knowledge related to nitrogen-containing compounds presents an important interest for the petroleum industry due to their implication in atmosphere pollution as well as their inhibitive or refractive behaviour towards hydroprocessing. Most of the nitrogenated species are concentrated in heavy petroleum cuts. As no analytical method is resolutive enough for these heavy cuts, particularly regarding nitrogen-containing compounds, a new approach is needed. For this reason, this study focuses on the development of a GC × GC technique, through the hyphenation of a specific NCD detector with a GC × GC system at high temperature. The performances of highly polar thermally stable stationary phases, in particular those composed of promising ionic liquids, were monitored in normal and reversed configurations. Subsequently, after the extraction of neutral or basic compounds by adsorption on an ion-exchange resin, a first quantitative determination was attempted for a straight-run and a direct coal liquefaction vacuum gas oils. This study led to a better understanding of the behaviour of highly aromatic N-compounds by 2D-GC including an ionic liquid phase as well as a deeper N-characterization of heavy petroleum fractions.

A novel approach for characterization of polycyclic aromatic hydrocarbon (PAH) pollution patterns in sediments from Guanabara Bay, Rio de Janeiro, Brazil

A novel multivariate method based on principal component analysis of pre-processed sections of chromatograms is used to characterize the complex PAH pollution patterns in sediments from Guanabara Bay, Brazil. Five distinct sources of 3- to 6-ring PAHs could be revealed. The harbour is the most contaminated site in the bay, its plume stretches in a South West to North East direction and the chemical profile indicates mainly pyrogenic sources mixed with a fraction of high-molecular-weight petrogenic PAHs. Rio São João de Meriti is the second largest source of PAHs, and introduces mainly a fraction of low-molecular-weight petrogenic PAHs from the western region of Rio de Janeiro. The sites close to the ruptured pipeline at the Duque de Caxias Refinery show a distinctive pollution pattern indicating a heavy petroleum fraction. The method also led to the identification of new potential indicator ratios also involving coeluting peaks (e.g., triphenylene and chrysene).

Advances in Quantitative Analysis of Heavy Petroleum Fractions by Liquid Chromatography−High-Temperature Comprehensive Two-Dimensional Gas Chromatography: Breakthrough for Conversion Processes

The implementation of high-temperature two-dimensional gas chromatography (HT-2D-GC) represents an important advance for heavy petroleum fraction analysis. Offline liquid chromatography (LC) separation before HT-2D-GC was applied to different vacuum gas oils (VGOs); results were in agreement with those obtained from reference methods. These conditions allowed for an extended quantification of heavy saturated compounds, including iso-paraffins and naphthenes. Weight distributions by carbon atoms number and chemical structures could be built for VGO cuts thanks to this innovative separation. These breakthrough progresses for the characterization of heavy petroleum fractions represent utterly new data to study conversion processes (including coking and hydrotreatment/hydrocracking) and to improve kinetic models, which could be based on actual chemical composition.

Tracking aromaticity changes in heavy hydrocarbon processing by monitoring changes in electrical resistivity

In this work, the changes in electrical resistivities of a vacuum residuum are analyzed to determine pyrolysis reaction rates at different temperatures during high temperature processing. Fractions of the residual oil from vacuum distillation were treated at a constant and uniform temperature, and electrical resistance was related to aromaticity. The results show that resistivity behaves like a first order decay-like thermal cracking reaction. This method could replace chemical methods used to determine the temperature necessary for thermal cracking reactions and the kinetic parameters of heavy petroleum fractions.

Observation of Liquid Crystals in Heavy Petroleum Fractions

In this work, we report for the first time the observation of naturally occurring discotic liquid-crystalline domains of ca. 100 μm in diameter in unreacted heavy fractions of petroleum. Precipitated solids from several bitumen and heavy oil samples exhibited the characteristic optical patterns of liquid crystals when observed under cross-polarized light. Samples included asphaltenes precipitated from Athabasca and Cold Lake bitumen (Canada), Maya heavy crude oil (Mexico), and Safaniya crude oil (Saudi Arabia) and a maltene fraction of Athabasca bitumen. The liquid-crystal domains appeared in asphaltene solids at ∼330 K in a nitrogen atmosphere and disappeared at ∼430 K. Upon cooling and subsequent reheating, the domains did not reappear. Liquid-crystal domains also appeared and then disappeared in the presence of toluene vapor at room temperature. Because the liquid crystals exhibit both thermotropic and lyotropic behavior, they are amphotropic. While amphotropic liquid crystals are known to arise in biological systems, the specific attributes of the liquid-crystal structures observed here are the first reported occurrence of such behavior in nature. The presence of liquid crystals in petroleum solids enriches our understanding of the complex phase and interfacial behavior of these materials and may provide new opportunities for partitioning petroleum.

Extended characterization of a vacuum gas oil by offline LC‐high‐temperature comprehensive two‐dimensional gas chromatography

In a context of environmental preservation, purification and conversion of heavy petroleum cuts into high-quality fuel becomes essential. The interest for the characterization of those very complex matrices becomes a trendy analytical challenge, when it comes to get molecular information for the optimization of industrial processes. Among new analytical techniques, high-temperature 2-D GC has recently proved its applicability to heavy petroleum matrices, but lacks in selectivity to separate all chemical groups. To gain resolution, heart cutting is demonstrated for LC separation of saturated, aromatic and polar compounds prior to high-temperature 2-D GC. Therefore, an extended global resolution was obtained, especially by a better distinction of saturated compounds. This includes iso-paraffins and biomarker polynaphthenic structures, which are impossible to quantify with MS methods. This new way to analyze heavy petroleum fractions gives innovative opportunities for the construction of global weight distributions by carbon atoms number and by chemical families. This can right now be employed for quantitative analysis of heavy petroleum fractions and for studying conversion processes.

Characterization of Nitrogen-Containing Compounds in Heavy Gas Oil Petroleum Fractions Using Comprehensive Two-Dimensional Gas Chromatography Coupled to Time-of-Flight Mass Spectrometry

Nitrogen (N)-containing compounds are naturally present in petroleum, and they are responsible for several deleterious effects that reduce the quality of products and negatively affect the processes involved in the upgrading of feedstock. The speciation of such compounds in petroleum heavy fractions is still a challenge. In the present work, N-containing compounds were characterized in heavy gas oil (HGO) fractions using a solid−liquid fractionation scheme and comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. Classification and identification of compounds were carried out based on seven different categories of analytical information viz. retention times in first and second dimensions, analytical standards co-injection, the structured pattern of the separation space, the structured pattern of the separation space with the selection of specific m/z values, the library mass spectra match factor, and the characteristic deconvoluted mass spectra. All of these inter...

Heavy Petroleum Composition. 2. Progression of the Boduszynski Model to the Limit of Distillation by Ultrahigh-Resolution FT-ICR Mass Spectrometry

Heavy petroleum fractions are structurally and compositionally complex mixtures that defy characterization by many traditional analytical techniques. Here, we present the detailed characterization of a Middle Eastern heavy crude oil distillation series, in further support of the Boduszynski model, which proposes that petroleum is a continuum with regard to composition, molecular weight, aromaticity, and heteroatom content as a function of the boiling point. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides ultrahigh resolving power and mass accuracy and thereby allows for elemental assignment for each of the tens of thousands of peaks in a single crude oil sample. Part 1 of our five-part series established the validity of the Boduszynski model for the heavy vacuum gas oil (HVGO) distillation series. Here, we extend our analysis to fractions from a Middle Eastern heavy crude with cut temperatures including and beyond the middle distillate range. Collectively, the detailed com...

Fractionation of a coal tar pitch by ultra-filtration, and characterization by size exclusion chromatography, UV-fluorescence and laser desorption-mass spectroscopy

Ultra-filtration (UF) provides a new way of generating narrow bands of sample in the fractionation of coal and petroleum-derived liquids. It allows larger quantities of high-mass fractions to be recovered, making more detailed investigations possible, through the use of techniques requiring larger amounts of sample. In this work, UF-separated fractions have been used to study molecular mass distributions of a coal tar pitch, used as laboratory standard. The pitch was fractionated by solvent solubility into three fractions. These were further fractionated by ultra-filtration, using membranes specific to protein molecular sizes classed as “1 kDa”, “5 kDa”, “10 kDa” and “100 kDa”. Planar chromatography was used as a tertiary fractionation method, to sub-divide the UF-fractions. The various fractions were examined by size exclusion chromatography (SEC), UV-fluorescence spectroscopy and laser desorption-mass spectrometry (LD-MS). There was good agreement between mass estimates based on SEC and LD-MS of the smaller UF-fractions, with evidence for the presence of material with molecular masses ranging between 800 and 10,000 u. Examining the largest UF fractions of the pitch-pyridine-insoluble sample also gave clear evidence for material with molecular masses above 10,000 u. Taken together, however, the LD-MS data showed progressively diminishing differences, as the sizes of the UF membranes, and the likely molecular masses of the sample fractions, increased. One likely explanation is incomplete sampling during the laser desorption procedure. The evidence suggests that the upper mass limit detectable for these and similar samples by LD-MS has been reached. Despite these reservations, LD-MS appears as the best method to date, for investigating the mass ranges of samples derived from coal tar pitch and heavy petroleum fractions.

Knowledge of petroleum heavy residue potential as feedstock in refining process using thermogravimetry

In the petroleum industry, previous knowledge of the feedstock's potential to produce light material is an important aspect of refining. For the evaluation of heavy petroleum fractions, thermogravimetry (TG), a thermal analysis technique, is considered a good analytical tool to determine the thermal behavior of these fractions at high temperatures. In the present work, TG analyses were made of petroleum distillation residues from different Brazilian oils. The apparent cracking activation energy of saturates, aromatics, resins and asphaltenes was also determined by TG. Saturates and aromatics showed values of 80–120 kJmol − 1 at low conversions (< 0.3) and of 120–220 kJ mol − 1 at high conversions (> 0.3). The thermal cracking activation energy of resins and asphaltenes occurred between 220–300 kJ mol − 1 , i.e., at higher values than those of aromatic and saturated fractions. This paper discusses the prediction of carbonaceous residue based on thermal analysis.