Now showing 1 - 10 of 13
  • Placeholder Image
    Publication
    Eco-efficient method for the dissolution enhancement of heavy crude oil using ionic liquids
    (04-06-2016)
    Sakthivel, S.
    ;
    Velusamy, S.
    ;
    ;
    Environmentally friendly methods for oil and gas industries, e.g., use of aromatic and aliphatic based ionic liquids for the efficient dissolution of tank-bottom sludge, heavy crude oil, and pipeline wax deposition, were studied. The enhancement in the solubility of heavy crude oil in solvent and ionic liquids mixture was investigated. The dissolution of heavy crude oil was more in the solution with ionic liquid than with the solvent alone. Solubility of heavy crude oil in the presence of ionic liquids and in the solvents increased about 65% when compared with the solutions of heavy crude oil in solvents without ionic liquids.
  • Placeholder Image
    Publication
    Eco-efficient and green method for the enhanced dissolution of aromatic crude oil sludge using ionic liquids
    (01-01-2014)
    Sakthivel, Sivabalan
    ;
    Velusamy, Sugirtha
    ;
    ;
    The upstream petroleum industry faces operational and technical problems due to increased deposition of waxes, aromatics and asphaltene from crude oil sludge in oil storage tanks in the form of tank-bottom sludge (TBS). This results in huge production losses, and threatens environmentally safe operation; therefore, safer solutions are needed. In this work, nine aromatic ionic liquids (ILs) are synthesized and tested for the dissolution of TBS with the aid of five solvents, namely, toluene, heptane, decane, ethyl acetate and hexane. The UV absorbance values of the standard solutions (TBS in solvent) are compared with the sample solutions (TBS in solvent + ILs). It is observed that ILs significantly improve the dissolution of TBS in solvents compared with neat solvent alone. Different weight ratios of TBS : ILs (1 : 1, 1 : 0.5 and 1 : 0.1) are considered in this study. Ionic liquids (ILs) based on an imidazolium cation and various anions, such as [Cl]-, [Br]-, [BF 4]-, [H2PO4]-, [HSO 4]-, and [PF6]-, are considered in this investigation. It is observed that the dissolution of TBS in heptane in the presence of [HMIM]+[Br]- is efficient to a maximum extent of 66% with other solvents showing similar increased solubility effect with various ILs. In the case of hexane, it should be noted that the efficiency of dissolution of TBS goes on decreasing with increasing concentration of TBS in hexane. A hold-time study is also performed with heptane containing ILs and heptanes without ILs to determine the maximum time required for efficient dissolution of TBS. It is observed that the efficiency is increased beyond 66% in the presence of ILs for the dissolution of TBS in heptane, provided that the mixture of solvent and ILs are in contact with the TBS for a prolonged period of 30 days, or even longer as required. FT-IR and 13C-NMR spectral analyses are also performed so as to understand the efficiency of the ILs in the dissolution of TBS in various solvents, and it was observed that there is a decrease in the intensity of the peaks in the spectra of treated TBS with solvents, which is further enhanced by the addition of ILs. This journal is © the Partner Organisations 2014.
  • Placeholder Image
    Publication
    Investigation on the Effect of Ionic Liquids and Quaternary Ammonium Salts on the Kinetics of Methane Hydrate
    (01-01-2022)
    Gupta, Pawan
    ;
    Mondal, Smita
    ;
    ;
    This study investigates the kinetics of gas hydrate (methane gas) in the presence of Ionic Liquids (ILs) and organic Quaternary Ammonium Salts (QASs). Aqueous solutions of eight ILs (five aromatic ILs and three aliphatic ILs) and three QASs have been studied for the kinetics of methane hydrate formation. In this study, five aromatic-based ILs with cations, viz., 1-hexyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, and 1-octyl-3-methylimidazolium, and anions such as [Br]−, [Cl]−, and [HSO4]− were selected. Three aliphatic ILs with cations, viz., diethylammonium, tripropylammonium, and tributylammonium, attached with the [HSO4]− anion were also selected. In the case of QASs, varying carbon chain lengths such as tetra-n-methyl-, tetra-n-ethyl-, and tetra-n-butylammonium bromide (TMAB, TEAB, TBAB) have been considered for the study. The kinetics of methane hydrate formation were investigated at a pressure of 7.5 MPa and a temperature of 276.15 K in the presence of aqueous solutions of QASs at 0.05 mf (mass fraction) and 0.1 mf concentrations and ILs at 0.01 mf. The results show that 0.05 mf of TBAB assists the methane hydrate to nucleate very rapidly and enhances the rate of growth. Hence, TBAB at 0.05 mf is observed to be most promising for gas storage and gas separation/processing among all investigated QASs. TMAB and TEAB have shown slow kinetics; therefore, their presence in a gas hydrate system may not aid in hydrate gas storage/gas separation applications; nevertheless, they could be used as an inhibitor for the prevention of hydrates in systems where other inhibitors may become unsuitable. The aqueous solution of aromatic-based ILs generally shows hydrate promotion, except for shorter chain lengths. The shorter chain length of ionic liquid with suitable anion (Cl-) behaved as a hydrate as the inhibitor and with Br- as the promoter. In general, a bigger cation acts as a good nucleating agent. The anion [HSO4]− is common in both the categories of ILs (aromatic and aliphatic), and it looks like the hydrate inhibition (no hydrate formation) may have occurred due to its presence. ILs offer more scope to understand the tunability of cations and anions to derive a better solution for gas hydrate inhibition and promotion, which have more applications in the ares of methane storage and transportation.
  • Placeholder Image
    Publication
    Use of aromatic ionic liquids in the reduction of surface phenomena of crude oil-water system and their synergism with brine
    (28-01-2015)
    Sakthivel, Sivabalan
    ;
    Velusamy, Sugirtha
    ;
    ;
    Enhanced oil recovery is governed primarily by the role of interfacial tension between crude oil and water. Interfacial tension (IFT) of the crude oil-water system is one of the vital factors in the analysis of the capillary forces affecting trapped oil within the reservoir rocks. High salinity and temperature of the reservoirs tend to make researchers search for new surfactants to lower the interfacial tension in crude oil-water systems. The current study hopes to create a move toward solving the above problem through the use of aromatic ionic liquids (ILs) based on imidazolium as the cation and various anions such as [Cl]-, [Br]-, [BF4]-, [H2PO4]-, [HSO4]-, and [PF6]- in different concentrations. This work involves the study of the effect of concentration, temperature, time, and brine on the fate of surface tension (SFT) of water and interfacial tension of crude oil-water systems. The present study also addresses the trend in the electrical conductivity of ILs in water along with the effect of temperature and concentration of ILs. The study reveals that these ILs are effective in reducing the SFT and IFT of water and crude oil-water systems at high salinity and temperature conditions. In the IFT measurements, a linear decrement with increase in temperature is observed for crude oil-water in the presence of ILs. The interfacial tension of the various imidazolium-based ionic liquids with the crude oil-water system has been measured as a function of temperature by means of the Wilhelmy plate method. The influence of the nature of cation and anion of ionic liquids and of the chain length on the cationic head of the ILs on interfacial tension is also discussed in detail. At increased salinity conditions, unlike classical surfactants, these ILs are found to be more successful. Enhanced efficiency of the drop in IFT using NaCl and IL mixture has been confirmed by measuring the IFT between crude oil and the aqueous solution of IL. The synergism of salt and IL mixture on the reduction of IFT has been observed.
  • Placeholder Image
    Publication
    A robust model for the phase stability of clathrate hydrate of methane in an aqueous systems of TBAB, TBAB + NaCl and THF suitable for storage and transportation of natural gas
    (01-07-2016)
    Avula, Venkata Ramana
    ;
    ;
    Semiclathrate hydrates of natural gas have shown potential applications in natural gas storage and transportation. Promoters, viz., tetra-n-alkyl ammonium bromide (TBAB) and tetrahydrofuran (THF) have positive impacts on the phase stability condition in lowering the required pressure for hydrate formation. As part of this work, a predictive model for the phase stability of gas hydrate, which are necessary to understand the phase behavior of methane (CH4) hydrate in promoters, has been proposed. The fugacity of hydrate former in the gaseous phase is calculated from Peng-Peng-Robinson equation of state (PR-EoS), while the fugacity of water in the liquid phase is computed from recently proposed Pitzer-Mayorga-Zavitsas-Hydration (PMZH) model for TBAB system and non-random two liquid (NRTL) model for THF system. The van der Waals Plattew model is employed for the hydrate phase. The vapor pressure of water in the empty hydrate lattice as well as Langmuir adsorption constants have been expressed in terms of concentration of the promoters. The predictions of the proposed model are found to be match well with experimental data on phase stability of CH4 hydrate formed using TBAB and THF aqueous systems. Furthermore, the developed model is employed for the prediction of phase stability conditions of the semiclathrate hydrates of CH4 in TBAB + NaCl system. The developed model is found to interpret the promotion effects of both TBAB (with or without NaCl) and THF on phase stability conditions of CH4 hydrate. AARD-P% with PMZH model are observed to be 3.21% and 8.73% for semiclathrate hydrates of CH4 in TBAB and TBAB + NaCl, respectively, and 8.56% for clathrate hydrate of CH4 in THF. The model may be extended to evaluate the phase stability conditions of hydrates of multicomponent gas systems in TBAB/THF which are necessary for real field applications.
  • Placeholder Image
    Publication
    Spectroscopic investigations to understand the enhanced dissolution of heavy crude oil in the presence of lactam, alkyl ammonium and hydroxyl ammonium based ionic liquids
    (01-09-2016)
    Sakthivel, Sivabalan
    ;
    ;
    The deposition of crude oil in various production and surfaces facilities such as oil storage tanks in the form of tank-bottom sludge, pipeline deposition, skin formation at the near well-bore, deposition in the tubing leads to blockage which invites several operational challenges. These challenges, in turn bring about huge production losses, involvement of scarce human resources, and threatening the environmentally safe operation, thus needing safer solutions. An environmental-friendly method for the dissolution of heavy crude oil (HCO) with the use of ionic liquids (ILs) along with a paraffinic liquid hydrocarbon (organic solvent) is developed which is considered to be very helpful for easy pumping, reducing the risk of manual cleaning and time consumption. In this work, eleven ILs are selected from lactam, alkyl ammonium and hydroxyl ammonium families with various anions, such as, [HCOO]-, [CH3COO]-, [CF3COO]-, [C6H13COO]-. The results on the quantitative and qualitative dissolution of the HCO using organic solvents (with and without ionic liquids) are presented. Studies on the quantitative dissolution of crude oil are performed with the use of UV-vis spectrophotometer, while the qualitative information on the dissolution of HCO are carried out using FT-IR and 13C NMR techniques. In the case of sample system (HCO + solvent + ILs), the increase in solubility observed is up to a maximum of 80%. Time-hold study was conducted for a prolonged period of 30 days where the increase in solubility is improved in the range of 80-335% with the addition of ILs along with organic solvents, whereas standard system (without ILs), showed improvement in the range of 11-16% only. This method helps in increasing the efficacy of organic solvents, such as, the liquid hydrocarbons which would be suitable for upstream petroleum engineering application. Moreover, the used ionic liquids were recycled and can also be reused.
  • Placeholder Image
    Publication
    An improved model for the phase equilibrium of methane hydrate inhibition in the presence of ionic liquids
    (01-11-2014)
    Avula, Venkata Ramana
    ;
    ;
    In this work, a thermodynamic model is developed and used to predict the phase stability conditions for methane hydrate-ionic liquid (IL)-water system. The hydrate phase is computed from modified van der Waals-Platteeuw model. The Peng-Robinson equation of state (PR-EoS) and developed activity model as a combination of Pitzer-Mayorga-Zavitsas-hydration model is used to evaluate the fugacities of gas and liquid phases, respectively. The hydrate phase stability prediction is also computed using the liquid phase activity predicted by NRTL and Pitzer-Mayogra models, separately, and is compared with the results predicted from the developed model. The model predictions are compared with experimental results on the phase stability of methane hydrate reported in open literatures for 21 ILs. The 21 ILs chosen from various ionic groups such as tetraalkylammonium, pyrrolidinium, imidazolium cationic family with various anion group such as halides (Cl, Br, I), sulphate (HSO4, ethylsulphate), tetrafluoroborate (BF4) and dicyanamide (DCA). The absolute average relative deviation in predicted pressure (AARD-P) with developed Pitzer-Mayorga-Zavitsas-hydration-model is improved to 1.60% and non-random two liquid (NRTL), Pitzer-Mayorga model showed 2.02% and 1.77% with 120 data points in the temperature range of 272.1-291.59K and pressure range of 2.48-20.67MPa. For 120 data points of phase stability conditions of 21 ILs, 39.2% of the predicted equilibrium pressures (47 data points) were within relative absolute deviation of 0.0-1.0%, 29.2% of the equilibrium pressures (35 data points) were within absolute deviation of 1.01-2.5%, 25.8% of data (31 data points) were within 2.51-7.5% which are mainly for data with low concentrations of ILs and only 5.8% of data (7 data points) showed relative absolute deviations above 7.5% which are observed mainly for data with high concentrations of ILs. Further, the model is used to calculate the inhibition effect of selected 21 ILs on methane hydrate formation.
  • Placeholder Image
    Publication
    Adsorption of aliphatic ionic liquids at low waxy crude oil-water interfaces and the effect of brine
    (05-03-2015)
    Sakthivel, Sivabalan
    ;
    Velusamy, Sugirtha
    ;
    ;
    The need for development of better surface active agents for upstream oil and gas industry which can survive harsh condition of salinity are in great demand, particularly for the applications related to improved/enhanced oil recovery, flow assurance and oil and gas production operations keeping in mind the environmental constraints. The technical difficulties which need to be considered are those involving the surface forces such as surface tension (SFT) and interfacial tension (IFT) acting between the formation water and the low waxy crude oil. In this study, we have employed the use of eight aliphatic ionic liquids (ILs), based on di- and tri-alkyl ammonium as cations and with various anions such as [CH3COO]-, [BF4]-, [H2PO4]- and [HSO4]- for the investigation of the surface phenomenon of crude oil-water system. The synergistic effect of NaCl along with the ILs is investigated in detail. It is observed that there is a significant reduction in the surface tension of water and the interfacial tension of crude oil-water system in the presence of salt, particularly at higher concentration of NaCl (200,000ppm). Effect of temperature, time, alkyl chain length of the cationic part of the ILs, nature of anions of ILs and the concentration of ILs is also discussed. The trend in the electrical conductivity of aqueous IL solutions with various concentrations at three different temperatures 298.15-318.15K is also presented along with critical aggregation concentration. The study on the effect of ILs on the SFT/IFT of water and low waxy crude oil-water system reveal that the ILs are successful in minimizing the effect of the surface forces in the presence of salt and thereby, could pave the way for efficient enhanced oil recovery operations.
  • Placeholder Image
    Publication
    Thermodynamic modeling of phase equilibrium of carbon dioxide clathrate hydrate in aqueous solutions of promoters and inhibitors suitable for gas separation
    (01-09-2017)
    Avula, Venkata Ramana
    ;
    Gupta, Pawan
    ;
    ;
    Gas hydrates of CO2 in the presence of tetra-n-alkyl ammonium bromide (TBAB) and tetrahydrofuran (THF) show potential applications for storage. Prediction of the phase behavior of these systems is an important precursor for their successful application. In this work, a thermodynamic model is developed to predict phase equilibrium of CO2 hydrates in the presence of TBAB and THF aqueous solutions. In this work, the van der Waals and Platteeuw model is used to model the hydrate phase stability. The fugacity of hydrate former and that of water is calculated from the Peng–Robinson equation of state and the Pitzer–Mayorga–Zavitsas hydration (PMZH) model for TBAB and nonrandom two-liquid (NRTL) models for the THF system. Further, the vapor pressure of water in the empty hydrate as well as Langmuir adsorption constants has been expressed in terms of concentration of the promoter. The model predictions is compared with available experimental data on the phase equilibrium of CO2 hydrates in the presence of TBAB and THF aqueous solution and are found to be in good agreement. Then, the developed model is also applied for the prediction of phase equilibrium conditions of the semiclathrate hydrates of CO2 in the presence of TBAB + NaCl solution. The developed model is found to interpret the promotion effects of both TBAB (with or without NaCl) and THF on phase stability conditions of CO2 hydrate. The overall average absolute deviation in pressure has been perceived to be within 3.6% for TBAB and 7.7% for TBAB + NaCl both with PMZH model and 6.9% for THF systems with NRTL model. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. StartCopText© 2017 Curtin University of Technology and John Wiley & Sons, Ltd.
  • Placeholder Image
    Publication
    Experimental investigation on the effect of aliphatic ionic liquids on the solubility of heavy crude oil using UV-visible, Fourier transform-infrared, and 13C NMR spectroscopy
    (18-09-2014)
    Sakthivel, Sivabalan
    ;
    Velusamy, Sugirtha
    ;
    ;
    Chemical treatment of aromatic heavier hydrocarbons are traditionally done by using cyclic aromatic nonpolar solvents, such as benzene, xylene, and toluene, which have the capability to dissolve asphaltenes. However, these aromatic solvents are volatile and hazardous and hence not advisable to use. Alternatively, lighter hydrocarbons, such as heptane, hexane, etc., show lesser solubility. It is, therefore, crucial that these problems require intelligent, cost-effective, and innovative solutions. The present work investigates the possible solution for the dissolution of heavy crude oil using the application of eight aliphatic ionic liquids (ILs) along with five solvents, namely, toluene, heptane, decane, ethyl acetate, and hexane. Ionic liquids (ILs) based on [CH3COO]-, [BF4]-, [H2PO4]-, and [HSO4]- as anions and with various cations, such as di- and tri-alkyl ammonium, are considered. The enhancement in the solubility of heavy crude oil in solvent + ILs mixture is investigated using Ultraviolet - visible (UV - vis) spectrophotometry, Fourier transform-infrared spectroscopy (FT-IR), and 13C-nuclear magnetic resonance (NMR) spectroscopic techniques. The absorbance of the sample solution (heavy crude oil + solvent + IL) is compared with the standard solution (heavy crude oil in neat solvent alone). It is observed that the dissolution of heavy crude oil is more in the solution with IL than with the solvent alone. Solubility of heavy crude oil in solvents increases to about 70% in the presence of ILs. Hold-time study is also performed to understand the maximum time required for efficient dissolution of heavy crude oil. The hold-time study reveals that solubility of heavy crude oil in heptane increased to about 61-222% in the presence of ILs, as compared to 11-16% in the case of standard solution for a prolonged period of 30 days.