Taher A. Alsahhaf

Physical properties of heavy petroleum fractions and crude oils

Abstract Equations are provided for calculating boiling point, density, refractive index, critical temperature, pressure and density, acentric factor, surface tension and solubility parameter of single carbon number (SCN) hydrocarbon groups for C 6 -C 50 existing in crude oils and hydrocarbon-plus fractions. Results show good consistency among various properties and improvement over the values previously reported. These methods should enhance equation-of-state (EOS) predictions when experimental data are lacking.

Measurement and prediction of phase equilibria in the extraction of aromatics from naphtha reformate by tetraethylene glycol

Abstract The extraction of aromatics from naphtha reformate was carried out by the solvent tetraethylene glycol at six temperatures and three solvent to feed ratios. The concentrations of paraffins, naphthenes and aromatics in the extract and raffinate phase were measured and compared to values predicted by the UNIFAC group contribution model. It was shown that the UNIFAC model is capable of predicting the concentrations in this multicomponent system with an overall RMSD of 1.27 mol.%.

Retardation of asphaltene precipitation by addition of toluene, resins, deasphalted oil and surfactants

Abstract The aim of this work is to test the possibility of using deasphalted oil (DO) or resin (R) obtained from Kuwaiti crude to inhibit the asphaltene precipitation from such crude when n -heptane is added. The inhibition effect of toluene (T) and selected surfactants is also tested. Surfactants used are nonyl phenol (NP), dodecyl benzene sulfonic acid (DBSA), and dodecyl resorcinol (DR). The retardation of asphaltene precipitation with addition of inhibitor is found to be in the order: DR>DBSA>NP>R>T>DO. These results show that toluene and DO are not effective inhibitors. Their effect on the onset point becomes appreciable only when their mass fraction in the oil exceeds 60%. The resins have modest inhibition effect. The strong inhibition effect of the surfactants is due to the interaction between the acidic head of these molecules and the asphaltene. The mechanism of inhibition is explained in terms of the micellization model of Victorov and Firoozabadi. Onset point for asphaltene precipitation with n -heptane addition is calculated in the presence of different amounts of inhibitor. Calculated results agree well with experiment. It is possible by using the micellization model to predict the amount of inhibitor required for reaching a certain onset point.

A generalized method for estimation of critical constants

Abstract A generalized and simple method is proposed to estimate critical temperature, pressure and volume of both polar and non-polar compounds. The input parameters are normal boiling point, density and relative molar mass. The proposed procedure was used to estimate critical properties of more than 250 compounds including hydrocarbons (C1–C18), acids, sulfur compounds, nitriles, oxide gases, alcohols, halogenated compounds, ethers, amines and water. Average absolute deviations for estimation of critical temperature, pressure and volume for the proposed method are 0.9, 2.8 and 1.8%, respectively.

Vapor—liquid equilibria for the ternary system N2 + CO2 + CH4 at 230 and 250 K

Abstract Vapor—liquid equilibria for the ternary system N 2 + CO 2 + CH 4 were measured at 230 K and 6.205, 8.619 and 9.652 MPa, and at 250 K and 8.963 and 10.342 MPa. The data obtained in this work and available literature data on this system were predicted using the Peng—Robinson and the Patel—Teja equations of state. The application of the Peng—Robinson equation of state was performed with generalized parameters and with fluid-specific temperature-dependent parameters. The three methods gave similar results with no significant advantage in using the fluid-specific Peng—Robinson equation of state for this ternary system.

Bubble point measurements for the ternary system: Carbon dioxide, cyclohexane and naphthalene

Abstract Bubble point pressure data were measured for the binary system carbon dioxide, cyclohexane at 40, 60 and 80°C and for the ternary system carbon dioxide, cyclohexane and naphthalene at 75, 95 and 120°C. The ternary system measurements were determined at two constant cyclohexane to naphthalene mole ratios; 9:1 and 9:1.25 to study the effect of the presence of small amounts of naphthalene on the phase equilibria of carbon dioxide with cyclohexane. The data were represented by the Peng-Robinson equation of state with two temperature-independent interaction parameters. The agreement between the experimental and calculated results is relatively good with an overall absolute average deviation of 8%.

Effect of Inorganic Solids, Wax to Asphaltene Ratio, and Water Cut on the Stability of Water-in-Crude Oil Emulsions

The formation of stable water-in-crude oil emulsions during petroleum production and refinery may create sever and costly separation problems. It is very important to understand the mechanism and factors contributing to the formation and stabilization of such emulsions for both great economic and environmental development. This article investigates some of the factors controlling the stability of water-in-crude oil emulsions formed in Burgan oil field in Kuwait. Water-in-crude oil emulsion samples collected from Burgan oil filed have been used to separate asphaltenes, resins, waxes, and crude oil fractions. These fractions were used to prepare emulsion samples to study the effect of solid particles (Fe3O4) on the stability of emulsions samples. Results indicate that high solid content lead to higher degree of emulsion stability. Stability of emulsion samples under various waxes to asphaltenes (W/A) ratios have also been tested. These tests showed that at low W/A content, the emulsions were very stable. While at a wax to asphaltene ratio above 1 to 1, the addition of wax reduced emulsion stability. Stability of emulsion samples with varying amount of water cut has also been investigated. Results indicated that stability and hence viscosity of emulsion increases as a function of increasing the water cut until it reaches the inversion point where a sharp decline in viscosity takes place. This inversion point was found to be approximately at 50% water cut for the crude oils considered in this study.

Structural Characterization of Different Asphaltenes of Kuwaiti Origin

Abstract Asphaltenes obtained by precipitation from crude Kuwaiti oils have been analyzed by proton magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR) and Infrared (IR) spectral techniques. The molecular weight and elemental analysis were also determined. These combined analytical data were used for the characterization of these Kuwaiti oils. The asphaltenes molecular weights range from approximately 4200–6500 with an H/C ratio of 0.91–1.1 with an average 45–71% aromatic carbons. The average side chain length was of 4–6 carbons. It can also be concluded that the asphaltenes under investigation contain 5–9 sets of condensed aromatic rings joined together by bridges of alkyl chains or other hetero atoms and the average number of each of these sets of condensed aromatic rings is nearly 7. There are a number of alicyclic rings and condensed alicyclic rings in asphaltene. The IR spectra showed main molecular groups including OH, NH, SH, C=O and aliphatic and aromatic C-H′s.

Measurement of phase equilibrium in multicomponent systems of aromatics with n-methylpyrrolidone and predictions with unifac

Abstract Liquid—liquid equilibrium (LLE) of five binary and five ternary systems containing the solvent N -methylpyrrolidone (NMP) with different paraffins and aromatics were measured. The data presented in this work were used in the estimation of UNIFAC model interaction parameters between NMP and the main groups: CH 2 , ACCH 2 , ACH and CHNA. The estimated interaction parameters of these groups were used in conjunction with other interaction parameters presented in the literature to predict the phase equilibrium of NMP with a synthetic multicomponent system composed of paraffins, condensed naphthenes, monoaromatics and diaromatics. The results compare favourably with the experimental data measured in this work.

Salt effects on liquid–liquid equilibria in the partially miscible systems water+2-butanone and water+ethyl acetate

Abstract Liquid–liquid equilibrium data for the partially miscible systems of water+2-butanone+salt and water+ethyl acetate+salt were measured at 298.15 K. The salts used were potassium iodide, sodium bromide and lithium chloride. The systems were compared in terms of salting effect. The three-contribution electrolyte NRTL model is used to perform the data regression of the experimental data. New binary parameters are obtained. The calculated results are compared with the experimental data.