A Model for the Estimation of Surface Tension of Pure Hydrocarbon Liquids

Surface tension is an important property and its accurate prediction is required in most chemical engineering calculations. An equation for the surface tension of liquid hydrocarbons as a function of temperature is developed considering intermolecular attractions in liquid phase are reflected by its enthalpy. The model equation is validated with National Institute of Standards and Technology data on liquid hydrocarbon alkanes (C₁ to C₁₀ and C₁₂) accounting for molecular shape through sphericity factor. The molecular sphericity factor correlated well with molecular weight of the hydrocarbons. The accuracy of the proposed model equation is compared with the two empirical equations, and results showed that the proposed model equation predicts the surface tension of pure hydrocarbon liquids more accurately.     

New relation between viscosity and surface tension for pure hydrocarbon liquids

A new relation between viscosity and surface tension is proposed and checked for 21 pure hydrocarbon liquids, and validated with the National Institute of Science and Technology data. The performance and accuracy of the proposed relation are compared with the reported empirical correlations in the form of absolute average deviation. The proposed relation remains valid for higher hydrocarbons (up to C₂₅H₅₂). A total of 418 data points for 21 pure hydrocarbon liquids were taken into consideration for checking the accuracy of the proposed relation. The proposed relation gives an absolute average deviation of 5.66%, indicating high accuracy of the proposed relation.     

Permeability of foil based on exfoliated graphite to C1-C6 alkanes

The results of a study of C₁-C₄ alkane gas permeability and C₅-C₆ alkane and methanol vapor permeability through pressed foil based on exfoliated graphite with a density of 1 g/cm³ are presented. It has been found that the permeability of the studied graphite foil to C₄-C₆ hydrocarbons is higher than calculated values; in particular, reverse selectivity for pairs such as H²/hydrocarbon and N₂/hydrocarbon is observed. This can be due to a considerable effect of a surface flow on the total flow through the membrane.     

AN EXPERIMENTAL STUDY OF THE EFFECT OF PARAFFINIC SOLVENTS ON THE ONSET AND BULK PRECIPITATION OF ASPHALTENES

ABSTRACT

Asphaltene onset concentration and bulk deposition were measured for a typical live reservoir oil titrated with n-C₆H₁₄, n-C₅H₁₂, n-C₄H₁₀, C₃H₈, C₂H₆, CH₄ and CO₂ at 100° C (212 ° F) and 29.9 MPa (4340 psia). The concentration of titrant at asphaltene onset was observed to decrease approximately in a linear fashion with decreasing molecular weight of the paraffinic solvent; CH₄ did not induce any asphaltene precipitation. Bulk deposition experiments were performed using a solvent: oil volume ratio of 10:1; the results indicated that the weight percent of asphaltenes precipitated increased exponentially with decreasing molecular weight of the paraffinic solvents. More importantly, the asphaltene molecular weight showed a maximum for n-C₄H₁₀ precipitated asphaltenes. Possible explanations for this unusual result are presented.     

CHARACTERIZATION OF THIOLS IN PRESWEETENING AND SWEETENED RFCC GASOLINE DISTILLATE

ABSTRACT

Thiols in RFCC naphthas produced in two refineries in China have been separated and characterized with GC/FPD. The identification results show that there are more than 20 kinds of thiols, including C₃-C₈ normal thiols, isothiols, thiophenol and methylthiophenol presenting in presweetening RFCC naphthas, while in sweetened RFCC naphthas, only have the isothiols and C₇-C₈ normal thiols been detected. The content of C₇-C₈ thiols and isothiols is higher in RFCC naphthas than that in FCC naphthas.     

Exhaustive schemes for refining C<Subscript>3</Subscript>-C<Subscript>4</Subscript> hydrocarbon fractions

Exhaustive schemes for efficient refining of the C₃-C₄ hydrocarbon fraction using zeolite type Y catalysts to obtain a high-octane additive are proposed. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 6–7, September–October, 2008.     

Desulfurization From Model of Gasoline by Extraction With Synthesized [BF4]−- and [PF6]−-based Ionic Liquids

Abstract

The authors report that 1-octyl-3-methylimidazolium tetrafluoroborate, [OMIM][BF₄], and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF₆], ionic liquids were synthesized and tested for their capability to desulfurization from model of gasoline. The results show that the aromatic sulfur compounds with higher π-electron density were favorably adsorbed. The results also show that [BF₄]^?-based ionic liquid displays higher extraction efficiencies than [PF₆]^?-based ionic liquid. Thus, it was shown that the extractive ability of the imidazolium ionic liquids was dominated by the structure of cation and anion. It is also found that the sizes of ionic liquids are important factors affecting the absorption capacity for aromatic sulfur compounds.     

Modeling of formation of petroleum biomarker hydrocarbons by thermolysis and thermocatalysis of bacterium biomass

Thermolysis and thermocatalysis of the insoluble part of chemoorganoheterotrophic aerobic bacteria Arthrobacter sp. RV and Pseudomonas aeruginosa RM have been performed. The thermolyzates and thermocatalyzates of these bacteria contain the hydrocarbon biomarkers n-alkanes, isoprenanes, steranes, and terpanes. Of n-alkanes, the C₉-C₃₅ hydrocarbons with unimodal distribution formed in the products of or C₉-C₃₉ n-alkanes with bimodal distribution are produced by thermolysis or thermocatalysis, respectively. n-Alkanes with odd number of carbon atoms in the molecule prevail over the even counterparts (n-C₉, n-C₁₁, n-C₁₅, and n-C₁₇) in the thermolysis products of both strains, whereas n-alkanes with even number of carbon atoms (n-C₁₆, n-C₁₈, and n-C₂₀) dominate in the thermocatalyzates. Isoprenanes of the C₁₃-C₂₀ composition are generated. It is noteworthy that regular C₁₇ isoprenane has been found for the first time among isoprenanes. The cyclic biomarker hydrocarbon steranes and terpanes are simultaneously generated, with the distribution of C₂₇-C₂₉ regular steranes resembles that in marine oils generated in argillaceous strata. At the same time, the adiantane to hopane ratio (H₂₉/H₃₀) is characteristic of the organic matter generated in carbonate strata.     

Generation of adamantanes and diamantanes by thermal cracking of high-molecular-mass saturated fractions of crude oils of different genotypes

The thermal cracking of high-molecular-mass paraffin-cycloparaffin fractions (bp above 350°C) of oils of different genotypes was carried out. Although the >350°C fraction contains neither adamantanes C₁₀-C₁₄ nor diamantanes C₁₄-C₁₆, which boil in the range 190–286°C, they are generated again during the thermal cracking of high-molecular-mass paraffin-cycloparaffin fractions. Thus, it was first shown that hydrocarbons with the adamantane and diamantane moieties are present in the >350°C fraction. The distribution of C₁₀-C₁₃ adamantanes in crude oils correlates well with that in the products of the thermal cracking of high-molecular-mass (>350°C) saturated fractions, thus indicating a relation between the high-molecular-mass hydrocarbon portion containing the adamantane moiety and C₁₀-C₁₃ adamantanes in the oils. There is no such correlation for the distribution of diamantane hydrocarbons of the C₁₄-C₁₆ series.     

Mechanochemical processing of oil residues

The feasibility of processing heavy-oil resid by mechanochemical action is explored. It is shown that hydrocarbon destruction and condensation processes occur in equal measure. The n-paraffins C₆-C₁₆ are subject to destruction, and the condensation processes are associated with alkylation of aromatic hydrocarbons by paraffin-destruction products. C₁₆₊ paraffins are formed during mechanochemical destruction of the paraffins.     

The Prediction of Asphaltene Precipitation from Crude-Oils

Abstract

Asphaltene precipitation is undesirable deposition that causes difficult problems in oil production and transportation. A molecular thermodynamic model is proposed for predicting the asphaltene precipitation under live oil conditions and at a wide range of pressures and different solvent ratios. In this model, it is assumed that the precipitation phenomenon is a reversible process, and an equation of state is employed for phase behavior prediction. The vapor and liquid equilibrium calculations are performed separately and sequentially. The characterization of unknown-heavy fraction of petroleum (C₇₊) is obtained by the generalized molar mass distribution model, in which C₇₊ is represented by four pseudocomponents. The two heaviest pseudocomponents of C₇₊ are identified as asphaltenic components, are also considered as precipitating components. The model is verified by its ability to prediction of asphaltene precipitation in different thermodynamic conditions. It has been shown that the calculated results are in good agreement with the experimental data.     

THERMAL DECOMPOSITION OF SAUDI CRUDE OIL ASPHALTENES

Abstract

Asphaltenes precipitated by the use of pentane, heptane and decane solvents from Saudi Arabian Light (AL) and Saudi Arabian Heavy (AH) crude oils 370^°C + residua have been investigated by thermal gravimetric analysis and pyrolysis - gas chromatographic analysis at 350^°C and 520^°C. Gas chromatographic analysis of the gases evolved during pyrolysis has shown that CO, CO₂ and CH₄ constitute the major portion of the gases evolved at 350^°C from pentane and heptane asphaltenes of AH residue and from pentane asphaltenes of AL residue. Whereas gases evolved from decane asphaltenes are dominated by CO₂ and C₂-C₄ hydrocarbon gases. At 520^°C, hydrogen and methane represent 56-80 vol %of the gases evolved from all the four asphaltenes. The amounts of C₁-C₄ hydrocarbon gases increased with an increase in the carbon number of the precipitating solvent at 350^°C and decreased at 520^°C. The presence of up to C₃₆ normal alkane hydrocarbon has been indicated in the maltenes produced from these asphaltenes. The loss of nitrogen from AH asphaltenes during pyrolysis remained low (1-6 wt %), whereas the losses of oxygen and sulphur ranged from 58 to 74 wt % and 10 to 29 wt %, respectively.     

New Statistical Concepts for Prediction Viscosity,Critical Temperature,and Critical Pressure of Homologous Hydrocarbon Series (C n H2n+2)

Abstract

A new model for prediction viscosity, critical temperature, and critical pressure for homologous hydrocarbon series C _n H_2n+2 as a function of carbon number only. The new model has a general formula: η or T _c or P = A ₁ C ^{A ₂} (2+2C) ^{A ₃} . This new model provides accurate and computationally reliable prediction for the corresponding properties (η, T _c , and P _c ) value.     

New model calculates solubility of light Alkanes in triethylene gycol

New model, which cover the full range of dehydration-plant operating conditions and wide range of experimental data results, estimate the amount of CH₄, C₂H₆ and C₃H₈ absorbed per volume of triethylene glycol (TEG) circulated vs. the reduced partial pressure of light Alkanes and the absorber reduced temperature. TEG has a tendency to remove the hydrocarbons. Hydrocarbon solubility is a major factor when considering the use of a physical solvent. Quantifying this amount of absorption is critical in order to minimize hydrocarbon losses or to optimize hydrocarbon recovery. This article provides comparisons with experimental data.     

Saturated hydrocarbons of Ulyanovsk oblast crude oils and waxes isolated from these oils

The composition and distribution of saturated hydrocarbons (alkanes, steranes, and terpanes) of oils from the Ulyanovsk oblast of the Volga-Urals oil-and-gas basin were studied. Wax fractions were isolated from crude oils, and C₄₈-C₅₂ high-molecular-mass n-alkanes, C₃₅-C₅₂ alkylcyclopentanes, and C₂₄-C₄₂ 2- and 3-monomethylalkanes were identified in these fractions. Based on the data on the composition of C₁₀-C₃₆ n-alkanes, C₁₉-C₃₅ terpanes, C₂₁-C₃₀ steranes, and C₄₀₊ alkanes, it was shown that the oils in question were generated by marine organic matter in carbonate sediments. Oil from the Novolabitovskoe field (1981–1992 m) substantially differs for the other oils in terpane and sterane compositions. These differences are supposedly due to another source of organic matter.     

The Effects of Weight Hour Space Velocity on the Products Distribution of Aromatization Reaction of Lanlian FCC Gasoline

Abstract

By using Lanlian fluid catalytic cracked (FCC) gasoline as a feedstock, the effects of weight hour space velocity (WHSV) on the product distribution, light oil compound, off-gas, and liquefied petroleum gas were researched in a confined fluidized bed reactor. The equation of off-gas yield, liquefied petroleum gas yield, coke yield, and light oil yield with increasing WHSV were established in the experimental data. The experimental result showed that with increasing WHSV, coke, off-gas, and liquefied petroleum gas yield decreased gradually, and light oil yield increased piece by piece; the amount of olefin was enhanced step by step, that of aromatics dropped slowly, and that of saturated hydrocarbon did not change. However, olefin conversion and increasing ratio of aromatics presented a slowly decreasing trend and increasing ratio of saturated hydrocarbon showed no change; hydrogen yield was low and did not change; i-butane and propane decreased, but n-butane increased gradually; C⁰ ₃/C⁼ ₃ and nC⁰ ₄/nC⁼ ₄ values did not change, iC⁰ ₄/iC⁼ ₄ variety had no order; C⁰ ₃/C⁼ ₃, C⁰ ₄/C⁼ ₄, and (C⁰ ₃ + C⁰ ₄)/(C⁼ ₃ + C⁼ ₄) values showed a decreasing trend.     

Effect of process conditions on Fischer–Tropsch synthesis product selectivity over an industrial iron-based catalyst in slurry reactor

The authors present the application of the statistical model in CO hydrogenation to CH₄, C₂-C₄ and C₅₊ over industrial iron-based catalyst (100 Fe/5 Cu/4.2 K/25 SiO₂) in a 1-L stirred tank slurry reactor. The effect of different reaction conditions, including temperatures (T = 493, 513 and 533 K), pressures (P = 0.8, 1.5, 2.25, and 2.5 MPa), synthesis gas feed molar ratios (H₂/CO = 0.67 and 2), and gas space velocity (GSV) from 0.52 to 23.5 Ndm³/g-Fe/h on selectivity investigated via a statistical models. The proposed selectivity model is very useful in the oil, gas, and petrochemical industries and can be used for interpretation of experimental data, comparison of performance of different reactor conditions, and reactor modeling and simulation studies. Furthermore, interaction between operating parameters such as pressure, temperature, H₂/CO, and GSV was investigated in selectivity models. A CUBIC polynomial was successfully fitted to the experimental data. It was concluded that C₅₊ selectivity shifts to higher with increasing total pressure (H₂/CO) ratio and decreasing temperature. Decreased H₂/CO ratio and temperature and increasing in the reactor pressure cause CH₄ formation decrease. Temperature and pressure fluctuations vary product distribution. As it is observed, the insignificant term in C₂-C₄ selectivity is pressure. With the models obtained from regression we can reach to the optimum condition for favorite products such as C₂-C₄ or C₅₊. So that optimization must be done to illustrate the optimum conditions. It was obtained that the maximum amount of C₅₊ and C₂-C₄ and minimum amount of methane achieved in T = 528.97 K, P = 1.23 bar, H₂/CO = 2, and GSV = 23.49 Ndm³/g-Fe/h.     

The formation of the composition of unrecovered oils in producing oil fields of Tatarstan

Analysis of the composition of unrecovered and produced oils of Tatarstan shows that the adsorption-chromatographic process upon oil motion in the reservoir during recovery is manifested in an increase in the density and viscosity of unrecovered oils. They do not contain light hydrocarbons of the IBP ?200°C fraction and have dramatically smaller concentrations of both the least polar lube oil hydrocarbons and alcohol-benzene-extractable resins exhibiting the highest polarity. According to GLC data, unrecovered and produced oils are classified with different subtypes of chemical type A1 of nonbiodegraded oils: produced oils are grouped with subtype 1 and unrecovered oils are attributed to subtype 2. The dynamics of the development of areas of produced oils with the use of a technique based on the activation of reservoir microflora showed that the process of the microbiological oxidation manifests itself in the preferential ability of reservoir microflora to digest C₁₂-C₃₄ n-alkane hydrocarbons as compared to cyclic hydrocarbons. Normal C₁₂-C₂₀ alkanes are consumed by bacteria before hydrocarbons with a greater number of carbon atoms C₂₀-C₃₄ of this series. An analysis of extracts from aqueous infusions of oils showed that the dissolution process leads to the transfer of 0.04–0.07 wt % hydrocarbons and heteroatomic components from oil to water.     

Simple Correlation Estimates Critical Properties of Alkanes

Abstract

A simple exponential model is proposed to estimate the critical temperature, pressure, and volume of alkanes as a function of normal boiling point and molecular weight. The proposed correlation was used to estimate critical properties of 30 compounds including (C₁?C₃₀) of alkanes. The associated parameters were estimated by fitting model to experimental data using nonlinear regression analysis to minimize the sum of squares error employing a trust-region algorithm of MATLAB software and a BFGS algorithm of a solver add-in program in Microsoft Excel. Comparison showed superiority of the proposed model over previous proposed models. The average absolute deviation for estimation of critical temperature, pressure, and volume of the proposed correlation were 0.49%, 1.16%, and 0.97%, respectively.     

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation,we designed hydrous pyrolysis experiments on Type-II kerogen samples,supposing that the water and water–mineral interaction play a role.U-ore was set as the variable for comparison.Meanwhile,anhydrous pyrolysis under the same conditions was carried out as the control experiments.The determination of liquid products indicates that the presence of water and minerals obviously enhanced the yields of C_(15+) and the amounts of hydrocarbon and nonhydrocarbon gases.Such results may be attributed to waterorganic matter reaction in the high-temperature system,which can provide additional hydrogen and oxygen for the generation of gas and liquid products from organic matter.It is found that δD values of hydrocarbon gases generated in both hydrous pyrolysis experiments are much lower than those in anhydrous pyrolysis.What is more,δD values are lower in the hydrous pyrolysis with uranium ore.Therefore,we can infer that water-derived hydrogen played a significant role during the kerogen thermal evolution and the hydrocarbon generation in our experiments.Isotopic exchange was facilitated by the reversible equilibration between reaction intermediaries with hydrogen under hydrothermal conditions with uranium ore.Carbon isotopic fractionations of hydrocarbon gases were somehow affected by the presence of water and the uranium ore.The increased level of i-C_4/n-C_4ratios for gas products in hydrous pyrolysis implied the carbocation mechanism for water-kerogen reactions.