Distillation Cuts Research Articles

Low temperature behaviour of refined products from DSC measurements and their thermodynamical modelling

The low temperature behaviour of five distillation cuts (230–375°C) from crude oil from different sources (North Sea, Africa and Middle East) provided by the Portuguese refinery Petrogal, was studied. Precipitation curves for these cuts, showing the evolution of the fraction of solid n-alkanes with temperature, were measured by DSC and the compositions of the cuts were analysed by gas chromatography (GC). The measured precipitation curves have been compared with the predictions from a thermodynamical model using the compositional analysis. The model results agree well with the experimental data indicating that the model used can be an adequate tool to predict the low temperature behaviour of refined oil products.

THE EFFECT OF PARAFFINIC FRACTIONS ON CRUDE OIL WAX CRYSTALLIZATION

The influence of the concentration and type of paraffinic crude oil components on the wax appearance temperature (WAT) was evaluated by means of Polarized Light Microscopy. High pour point waxy crudes were doped with paraffin distillation cuts, and changes on cloud points permitted to assess the inefficiency of a polymeric commercial paraffin inhibitor for crudes rich in heavy paraffins. An insensitive crude oil upon the addition of wax inhibitors was fractionated into its hydrocarbon type fractions. Light components were distilled out as the C24 − constituents. C24 + cyclo/iso and linear paraffins were isolated from the distillation residue s saturates by means of 5 Å molecular sieves adduction. The effect of virgin crude oil enrichment with the cyclo/isoparaffins fraction on its cloud point and a polymeric paraffin inhibitor efficiency were evaluated. These components have no significant impact on the inhibitors efficiency at concentrations below 40 wt%, but they increase the crude oil cloud point above 50 wt%, as a consequence of the higher average molecular weight introduced by these components. At this high concentration, a crystal modifier activity enhancement was observed, probably caused by steric hindrance of naphthenic and branched structures. The linear paraffin fraction with more than 24 carbon atoms (nC24+), also isolated from the virgin crude oil, was used for doping experiments on reconstituted crude samples, containing all the original components except this particular fraction. A direct dependence between the cloud point and the concentration of this fraction was assessed.

DISTILLATION CHARACTERISTICS AND COMPOSITIONAL ANALYSIS OF ARABIAN LIGHT STRAIGHT RUN NAPHTHA

ABSTRACT Straight run naphtha is a basic constituent of refined petroteum products. It consists mainly of aliphatic hydrocarbons along with small amounts of naphthenic and aromatic hydrocarbons. It has a wide boiling range between 95°F and 410°F. Currently, its main utilization is as gasoline blend, however, naphtha is a potential feedstock for the production of various petrochemicals. Continuous catalytic reforming of naphtha can produce aromatic compounds in amounts up to 70% of the reformat. Nevertheless, the catalytic reforming process is usually associated with various limitations that may be related to the wide-ranging composition of naphtha. In this study straight run naphtha derived from Arabian Light crude oil was fractionated, and the hydrocarbon composition of its different distillation cuts was determined. The results indicate that, straight run naphtha can be split into two main fractions. A light fraction boiling between ambient temperature and 225°F, consists mainly of C7 (−) and a medium heavy fraction boiling between 225°F and 335°F, consists mainly of C7 (+). Detailed distillation characteristics, along with compositional analysis of SRN seems to be useful for diversifying its processing technologies, and upgrading currently applied processing practices to yield various high-value products and petrochemicals feed stocks.

Speed of sound, density, and compressibility of petroleum fractions from ultrasonic measurements under pressure

The speed of sound in a synthetic and a real distillation cut has been measured up top= 150 MPa in the temperature rangeT= (293.15to373.15) K. The synthetic system, which is representative of distillation cuts, is made up of five components with high boiling point temperatures of aboutTb= 523 K belonging to essential chemical families found in natural fluids {iso, or n-paraffins, naphthenes, and aromatics (alkybenzene, or alkylnaphtalene)}. The distillation cut comes from the separation of a standard crude oil by distillation aroundT= 523 K. The measurements allow the evaluation of various thermophysical properties such as densities, and isentropic and isothermal compressibilities up top= 150 MPa with the help of additional density measurements performed at atmospheric pressure.

SURFACTANT-OIL-WATER SYSTEMS NEAR THE AFFINITY INVERSION. PART XI. pH SENSITIVE EMULSIONS CONTAINING CARBOXYLIC ACIDS

ABSTRACT Surfactant-oil-water systems in which the surface active substance is a mixture of carboxylic acid and its sodium salt (soap), exhibit emulsion property maps that are consistent with the phase behavior and the general emulsion phenomenology. However they present specific features such as an extended C+ multiple emulsion region and a skinked A+ W/O emulsion zone. In this case the aqueous phase pH drives the relative hydrophilicity of the acid/salt mixture at interface and plays the role of the most sensitive formulation variable. Studied systems contain C10 to C14 carboxylic acid, NaCl brine and a light distillation cut, as well as alcohols.

Thermophysical properties of petroleum distillation fractions up to 150 MPa. Comparative analysis of some equations of state

Speed of sound, density, compressibilities (isoentropic/isothermal) have been measured up to 150 MPa in the temperature range (293.15–373.15) K in two distillation cuts. The data obtained are compared with the values predicted by means of several equations of state.

Effects of time of grape pomace fermentation and distillation cuts on the chemical composition of grape marcs

The effects of fermentation time and distillation cuts on the composition of distillates in terms of ethanal, 1,1-diethoxyethane, methanol, 1-butanol, 2-butanol, 1-propanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate, ethyl 2-hydroxypropanoate, 3-methylbutyl acetate, hexyl acetate, 2-phenylethyl acetate, hexanol, trans-2-hexenol, trans-3-hexenol, cis-3-hexenol, 2-phenylethanol, ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl dodecanoate, 2-methylpropanoic acid, 3-methylbutanoic acid, hexanoic acid, octanoic acid, decanoic acid, and dodecanoic acid were assessed through data generated according to a factorial design using analysis of variance and principal component analysis. Four times of storage of pomace obtained following winemaking of two grape varieties of white Verde wine (Alvarinho and Loureiro) and three distillation cuts were considered; volatile compounds in the 24 samples generated were analyzed directly, and indirectly after extraction and concentration, by capillary gas chromatography. The results generated have suggested clear differences (P<0.05) between distillate cuts obtained throughout fermentation times for each grape variety. The major differences between the different distillate fractions analyzed were accounted for by the contents of diethyl butanoate, ethyl 2-hydroxypropanoate, and the sum of 3-methylbutanoic and 2-methylpropanoic acids for Loureiro, whereas the main differences were accounted for by the contents of diethyl butanoate and the sum of the carboxylic acids for Alvarinho.

Measurement and calculation of heat capacity of heavy distillation cuts under pressure up to 40 MPa

Isobaric heat capacities of natural mixtures were determined up to 40 MPa with a modified C-80 Setaram calorimeter equipped with cells designed for high pressures. The systems investigated were heavy distillation cuts with respective boiling points of 150, 200, 250 and 300°C. These experimental data were used as discriminatory values to test thermodynamic models and more precisely to choose among the great number of equations of state and mixing rules proposed in the literature, the most appropriate for the characterization of the heavy components.

Microbial desulfurization of a crude oil middle-distillate fraction: analysis of the extent of sulfur removal and the effect of removal on remaining sulfur.

Rhodococcus sp. strain ECRD-1 was evaluated for its ability to desulfurize a 232 to 343 degrees C middle-distillate (diesel range) fraction of Oregon basin (OB) crude oil. OB oil was provided as the sole source of sulfur in batch cultures, and the extent of desulfurization and the chemical fate of the residual sulfur in the oil after treatment were determined. Gas chromatography (GC), flame ionization detection, and GC sulfur chemiluminesce detection analysis were used to qualitatively evaluate the effect of Rhodococcus sp. strain ECRD-1 treatment on the hydrocarbon and sulfur content of the oil, respectively. Total sulfur was determined by combustion of samples and measurement of released sulfur dioxide by infrared absorption. Up to 30% of the total sulfur in the middle distillate cut was removed, and compounds across the entire boiling range of the oil were affected. Sulfur K-edge X-ray absorption-edge spectroscopy was used to examine the chemical state of the sulfur remaining in the treated OB oil. Approximately equal amounts of thiophenic and sulfidic sulfur compounds were removed by ECRD-1 treatment, and over 50% of the sulfur remaining after treatment was in an oxidized form. The presence of partially oxidized sulfur compounds indicates that these compounds were en route to desulfurization. Overall, more than two-thirds of the sulfur had been removed or oxidized by the microbial treatment.

Quantitative Extraction of Nitrogen Compounds in Oils: Atomic Balance and Molecular Composition

The aim of this study was to get an atomic mass balance on nitrogen compounds in petroleum fractions such as crude oils, distillation cuts, or rock extracts. Two methods have been developed for the separation of basic compounds: a liquid−solid extraction on a commercial acid-bound silica and a new technique by liquid−liquid extraction. Both methods allowed for a selective and quantitative recovery of the basic compounds. For neutral nitrogen species, a method is proposed based on deprotonation by a strong base and liquid−liquid extraction. The efficiency of the three methods was checked on appropriate standards. These techniques were then applied to a crude oil from the Middle East and its distillation cut 375−550 °C. All the basic and neutral fractions were submitted to elemental analyses in order to get the total nitrogen balance to be compared to the initial amount present in the crude oil. Results show that a large part of nitrogen is contained in the residue of the oil distillation above 550 °C. The...

Heat Capacity of a Synthetic Distillation Cut+n-Hexane System under Pressure

Isobaric heat capacities of synthetic mixtures were determined up to 40 MPa with a modified C-80 Setaram calorimeter equipped with cells designed for high pressures. The system investigated was a pseudo-binary hexane+synthetic cut, the latter consisting of compounds of the three chemical families that occur most frequently in natural effluents (paraffins, naphthenes and aromatics). The additional knowledge of density vs. pressure and temperature affords the specific heat γ ratio.

Relationships Between Storage Conditions of Grape Pomace and Volatile Composition of Spirits Obtained Therefrom

This study reports on the effects of addition of tartaric acid, addition of pectinase, time of anaerobic storage, and the storage container material on the concentrations of volatiles in marc distillates of <i>Alvarinho</i> and <i>Loureiro</i> varieties. The aim of this work is to predict how the concentration of every major volatile responds to each manipulated processing factor in each of three distillate cuts, a condition necessary to rationalize the process of the manufacture of <i>bagaceiras</i>. Fusel alcohols were, quantitatively, the largest group of flavor compounds in all cases, ranging from 395 to 2029 mg/L. Ethyl acetate and ethyl lactate were the most concentrated esters, ranging from 176 to 9614 and from 0 to 310 mg/L, respectively. Fermentation time is the manipulated variable that most strongly affected composition of marcs in terms of higher alcohols, while addition of pectinases and material of container are the manipulated variables that most strongly affected composition in terms of methanol (with a concentration range of 2694 - 6960 mg/L) and 2-butanol (with a concentration range of 0 - 279 mg/L). The effect of pectinase addition is statistically the most significant for the methanol content, whereas the effect of fermentation time is statistically the most significant for the 2-butanol content.

Determination of the Middle Distillate Fuel Potential of Shale Oil

Oil shale deposits constitute a large reserve of oil stocks. These immense deposits can potentially be used most conveniently as a source of middle distillate fuels such as jet fuel. The characteristic of the jet fuel distillation cut is a high n-alkane content. Jet fuels require a large n-alkane fraction in order to simultaneously meet both the freezing point and flash point requirements. The conditions reported in this study mimic the refining process known as delayed coking. This study focuses on a method for the rapid determination of the middle distillate fuel potential of shale-derived fuels.

ANALYTICAL APPROACH FOR THE DETERMINATION OF MOLECULAR WEIGHTS OF n-ALKANES IN CRUDE OIL DISTILLATION CUTS

ABSTRACT Average number molecular weights of linear alkanes found in the distillation cuts of a crude oil were indirectly investigated by vapor pressure osmometry, focusing the cuts that could not be completly analysed by gas chromatography. Experimental procedure consisted of separation of the saturates by liquid chromatography and selective oclusion of linear components therein in 5 Å molecular sieve, followed by measurement of the molecular weight of the combination of the remaining fractions and of the whole cut. Main results were the homogeneous molecular weights obtained for the components, including linear alkanes, in comparison to those of the correspondent whole cuts, which indicates that the knowledge of molecular weight of the latest ones is enough for the characterization of their components as to this parameter.

Medium-severity hydrotreating and hydrocracking of Israeli shale oil. 1. Novel catalyst systems

Novel catalysts were developed for the hydrodesulfurization, hydrodenitrogenation and hydrocracking of Israeli shale oil. They were designed to operate on feedstock containing a high level of sulfur and nitrogen. Two hydrotreating stages and one hydrocracking stage were performed in a batch reactor. High-activity catalysts with large macropores yielded 97 and 79% conversion of sulfur and nitrogen respectively in the first stage. 1H and 13C n.m.r. and nitrogen distribution measurements among the distillation cuts showed that nitrogen remaining after the first hydrotreating stage comprised low-molecular-weight heteroaromatics. A further reduction of the sulfur to 100–200 ppmw and nitrogen to 7–30 ppmw was obtained in the second stage using zeolite-containing catalysts. The major parameters affecting the catalyst performance were tested. A moderate temperature of 380°C and pressure of 15 MPa were used in both stages. A selective dual-zeolite hydrocracking catalyst in a third stage yielded 80% of the product in the naphtha boiling range.

Chemical flooding of oil reservoirs 5. The multiphase behavior of oil/brine/surfactant systems in relation to changes in pressure, temperature, and oil composition

Multiphase PVT-studies are conducted on surfactant-brine-oil systems relevant for oil recovery processes. An alkyl-o-xylene sulfonate is used as surfactant, NaCl-solution as brine, and various types of live oil, i.e. crude oil, fraction of crude oil, and model oil. Solubilization parameters for the microemulsion phase are determined in the temperature range of 40–180°C and the pressure range of 200–1000 bar. By increasing the pressure the trend in the phase behavior in all cases is II(+)/III/II(−). In the temperature scan the crude oil system showed a II(−)/III/II(+) phase behavior by increasing the temperature, while the model oil and the distillation cut of the crude oil without the heavy end fraction showed the opposite phase behavior, II(+)/III/II(−). The difference in the phase properties is discussed in terms of the resin-type compounds acting as cosurfactants, and the dissolution of water into the oil phase at high temperatures.

Three‐Stage wiped‐film molecular evaporator: Design and application

AbstractThis paper describes the design principles of multistage molecular evaporators with a wiped film which are used for gentle distillation of low‐volatility blends of thermolabile materials. The conditions of distillation in an evaporator with a convex evaporation surface are discussed, along with problems relating to the function of the segmented wiper in the formation of the retarded liquid film and the functional principles of closing elements in a multistage evaporator with a single evaporating cylinder and of the built‐in entrainment separator in the distillation space, which is designed to retain splashing spray. A TMO 65 three‐stage molecular evaporator is described, with an evaporating cylinder having a diameter of 65 mm and a total evaporating area of 0.19 m2. This pilot‐plant evaporator can be used in the small‐capacity production of specialty chemicals or in technological research as a verification unit for establishing data necessary for the operation of large evaporators. These possible applications are documented by the results obtained on fractionation of various important materials. Fractional distillation of crude monoacylglycerols (M) containing 35 to 55% M afforded concentrates containing over 90% M, at yields of 78 – 95% M in the product fraction. Fractionation of oligomers of higher α‐olefins gave distillate cuts with high contents of the respective n‐mer, suitable for use as synthetic lubricating oils. Fractionation of polyalkylaromatic residue from the production of monoalkylbenzenes produced a distillate fraction with excellent electrical insulation properties. Finally, purification of technical diane‐bis‐glycidyl ether yielded over 75% of a product fraction which was found suitable for production of insulating material for electrical equipment operating at voltages of 6 to 15 kV.

A DETAILED CHEMICAL ANALYSIS OF CHANGES TO BITUMEN PRODUCED BY THE IN SITU COMBUSTION PROCESS AT THE OXYGEN WOLF LAKE PROJECT, ALBERTA PART 2: DISTILLATION CUTS AND CHROMATOGRAPHIC FRACTIONS

ABSTRACT The detailed chemical changes in bitumen brought about over a one year period by an in situ combustion process in an oil sands reservoir have been investigated. The analytical data for the distillation cuts and chromatographic fractions from a core sample and a number of produced oil samples revealed significant changes as a result of the recovery process, particularly for the naphtha and middle distillate cuts. The residue cut did not exhibit any increase in heteroatom or asphaltene content. None of the changes to the produced oil samples would be expected to negatively impact on the subsequent upgrading process. The relationship between the observed changes to the fractionated oil samples and the dynamics of the in situ combustion process are discussed.

High-boiling fractions of crude from Tengiz field as raw material for lube oil production

Tengiz crude, as has been shown by classification studies [1, 2], is light, medium-sulfur, low-resin, and medium-wax. Its content of light fractions distilling below 350~ is 75-78% by weight, which is 1.5 times the content in the major West Siberian crudes. Therefore, it has been recommended that the Tengiz should be processed in the "fuel variant," i.e., primarily to obtain fuels. In order to evaluate the high-boiling fractions of Tengiz crude as a raw material for lube oil production, its atmospheric resid was subjected to vacuum distillation, taking 300-400, 400-450, and 450-500~ distillate cuts. The residue above 500~ (vacuum resid) was propane-deasphalted. Such distillates and deasphalted oil are commonly used as raw materials for the production of lube oil components. Judging from the data of Table 1, the Tengiz atmospheric resid has greater amounts of lube distillates but a considerably smaller amount of deasphalted resid in comparison with the atmospheric resids from largevolume West Siberian crudes [3]. Another distinctive feature of the Tengiz atmospheric resid is the gradual decrease of the lube distillate content with increasing boiling point. As a result, the content of low-viscosity distillate is more than twice that of viscous distillate or deasphalted oil. The comparatively low dewaxing yields from the distillates and deasphalted oil are evidence of higher wax contents in the original distillates and deasphalted oil in comparison with the analogous products from major medium-sulfur medium-wax crudes. The high density, refractive index, and specific dispersion that are observed for the dewaxed distillates and deasphalted oil can be attributed to specific features of their hydrocarbon composition (Tables 2 and 3): high contents of saturated hydrocarbons (47-54% by weight) and comparatively low contents of aromatic hydrocarbons with specific dispersion in the 125-160 interval. Because of the high content of isoparaffins (Table 4), we observe high viscosity indexes (120-140) for the saturated part, which is the main part of the oils. The saturated and aromatic hydrocarbons of the deasphalted oil from the Tengiz crude differ from the corresponding groups of hydrocarbons in the deasphalted oils from large-volume crudes that are used in lube oil production; also, the hydrocarbons from the Tengiz crude have lower viscosities. The heavy polycyclic hydrocarbons with specific dispersion above 160 have high densities and refractive indexes and very low viscosity indexes -a considerable difference from the properties of the corresponding hydrocarbons in major medium-sulfur medium-wax crudes. On the whole, the aromatic part of the Tengiz hydrocarbons includes considerable quantities of naphthenoaromatic hydrocarbons (10-11% by weight), aromatic hydrocarbons (15-16%), and sulfur-containing compounds (12-15 %). The sulfur is present mainly in the form of thiophene derivatives, along with thiocyclanes and sulfides.* The distillates and residue from vacuum distillation of the atmospheric resid of Tengiz crude are also characterized by high contents of resinous compounds, 7-11%, in comparison with the 4-5 % in the analogous products from vacuum distillation of atmospheric resids of other crudes that are used in lube oil production. The hydrocarbon groups that were segregated in these studies were blended to obtain samples characterizing the potential content of oils in both the distillate and residual stocks, with different levels of viscosity. The quality indexes of these products are listed in Table 5.

Naphthalene hydrogenation reactivity of rhodium-rhenium and ruthenium-rhenium formulations dispersed on doped titania carriers

The hydrogenation of naphthalene over Rh-Re and Ru-Re bimetallic catalysts, formulated on W 6+-doped TiO 2 carriers, is investigated in a slurry reactor at a temperature of 573 K and a pressure of 65 bar. It is shown that the hydrogen adsorption capacity of both catalysts increases with dopant concentration in the TiO 2 matrix, in the range 0–0.7 at.-%. Naphthalene hydrogenation activity is also enhanced as a result of carrier doping, especially of the Ru-Re catalyst. The activity of these catalysts in the hydrogenation of an actual coal-liquid distillate cut is also found to be superior, as compared to corresponding catalysts on undoped carriers or a commercial Co-Mo/Al 2O 3 catalyst.