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Novel or unconventional technologies are critical to providing cost-competitive natural gas supplies to meet rising demands and provide more opportunities to develop low-quality gas fields with high contaminants, including high carbon dioxide (CO2) fields. High nitrogen concentrations that reduce the heating value of gaseous products are typically associated with high CO2 fields. Consequently, removing nitrogen is essential for meeting customers’ requirements. The intensification approach with a rotating packed bed (RPB) demonstrated considerable potential to remove nitrogen from natural gas under cryogenic conditions. Moreover, the process significantly reduces the equipment size compared to the conventional distillation column, thus making it more economical. The prediction model developed in this study employed artificial neural networks (ANN) based on data from in-house experiments due to a lack of available data. The ANN model is preferred as it offers easy processing of large amounts of data, even for more complex processes, compared to developing the first principal mathematical model, which requires numerous assumptions and might be associated with lumped components in the kinetic model. Backpropagation algorithms for ANN Lavenberg–Marquardt (LM), scaled conjugate gradient (SCG), and Bayesian regularisation (BR) were also utilised. Resultantly, the LM produced the best model for predicting nitrogen removal from natural gas compared to other ANN models with a layer size of nine, with a 99.56% regression (R2) and 0.0128 mean standard error (MSE).

Desalination using hydrates is a developing field, and initial research promises a commercially feasible approach. The current study proposes the natural amino acid, namely tryptophan, as a biodegradable gas hydrate promotor for desalination applications to speed up the hydrate formation process. Its kinetic behavior and separation capabilities with CO2 hydrates were investigated. The studies were carried out with varying concentrations (0.5, 1, and 2 wt.%) of tryptophan at different experimental temperatures (274.15, 275.15, 276.15, and 277.15 K) at 3.5 and 4.0 MPa pressure and 1 wt.% brine concentration. The induction time, initial formation rates, gas uptake, and water recovery are characterized and reported in this work. Overall finding demonstrated that tryptophan efficiently acted as a kinetic hydrate promotor (KHP), and increased tryptophan quantities further supported the hydrate formation for almost all the studied conditions. The formation kinetics also demonstrated that it shortens the hydrate induction time by 50.61% and increases the 144.5% initial formation rate of CO2 hydrates for 1 wt.% addition of tryptophan at 274 K temperature and 4.0 MPa pressure condition. The study also discovered that at similar experimental conditions, 1 wt.% tryptophan addition improved gas uptake by 124% and water recovery moles by 121%. Furthermore, the increased concentrations of tryptophan (0.5–2 wt.%) further enhance the formation kinetics of CO2 hydrates due to the hydrophobic nature of tryptophan. Findings also revealed a meaningful link between hydrate formation and operating pressure observed for the exact temperature settings. High pressures facilitate the hydrate formation by reduced induction times with relatively higher formation rates, highlighting the subcooling effect on hydrate formation conditions. Overall, it can be concluded that using tryptophan as a biodegradable kinetic promotor considerably enhances the hydrate-based desalination process, making it more sustainable and cost-effective.

The intimidating level of anthropogenic CO2 in the atmosphere responsible for global warming and erratic weather conditions needs to be addressed on a priority basis. Different kinds of materials were used to capture CO2 to curtail the alarming and drastic effects of global warming. An ionic liquid (IL) 1-butyl-3-methylimidazolium methanesulfonate [C4mim][CH3SO3] was chosen, owing to its unique and efficient characteristics required for CO2 capture. Thermos-physical characteristics such as sigma surface, sigma profile, and sigma potential are calculated from the COSMO-RS model independent of any kind of experimental or coefficient data as an input. The mandatory information required for the interaction of IL with CO2 was obtained from this model. The COSMO-RS model depends upon unimolecular quantum chemical analysis associated with statistical thermodynamics, molecular structure, and conformation. The structural confirmation of [C4mim][CH3SO3] IL was performed by FTIR, 1H NMR, and 13C NMR spectroscopic methods. Spectrochemical properties are calculated by FTIR, NMR, UV-visible, and fluorescence. Maximum CO2 solubility performed at room temperature (RT) and 45 bar was found to be ~2.7 mmol/g. The uptake of CO2 indicates the presence of sulphur-functionalized anions and bulky alkyl groups in IL’s significant affinity towards CO2. According to hysteresis-based classification, CO2 sorption and desorption follows type H3 classification, which indicates the presence of microporous and mesoporous in the IL sample. The effect of functionalized anions and alkyl groups on CO2 capture is highlighted in this study. The present study is aimed at providing a detailed overview related to theoretical and experimental study and application in terms of CO2 capture of IL.

In this work, CO2 absorption from simulated biogas is investigated using different blends of a PZ + AMP solution in an absorption system at CO2 partial pressures ranging between 20 and 110 kPa. The collected data were presented as CO2 removal profiles along the packed column and were evaluated in terms of CO2 removal efficiency (%) and average overall volumetric mass transfer coefficient in the gas phase (KGav¯). An increased PZ concentration in the AMP solution was found to significantly increase the CO2 removal efficiency and KGav¯ values. It was observed that, when conducted at different CO2 partial pressures, gas and liquid flow rates, and chemical concentrations, the Lamine/GCO2 ratio strongly influenced the process behaviour in the packed column. Additionally, the optimal inlet liquid temperature was observed to be 35 ± 2 °C in this study.

This paper presented the effect of CO2concentration in the gas feed to the CO2absorption performance using a green solvent, potassium carbonate promoted with glycine (PCGLY). Recently, the performance of this solvent (with precipitates) was hindered by its poor mass transfer performance due to the blockage in packings and piping. Therefore, this study focused to study the CO2 absorption performance of non-precipitating potassium carbonate promoted with glycine. This green solvent contains aqueous blend of 15wt% potassium carbonate and 3 wt% glycine. The absorption performance of the solvent was obtained by demonstrated a few experimental works using a bench scale packed absorption column. The packing type was Sulzer metal gauze and the column consisted of six sampling point which located equidistance along the packing.The effect of CO2 concentration at the gas feed was assessed in term of its CO2 removal efficiency and concentration profile along the packing. The study shows the decreasing trend of CO2 removal as CO2 inlet concentration in the gas feed increases. The reason of this behavior is due to the limited reactant of liquid phase to absorb high CO2concentration in gas phase. The main outcome of this study demonstrated the efficient absorption which can absorb up to 79.24 % of CO2from natural gas using non-precipitated PCGLY.

In this study, series of non-ionic surfactants from Span and Tween are evaluated for their ability to affect the viscosity profile of cyclopentane hydrate slurry. The surfactants, Span 20, Span 40, Span 80, Tween 20, Tween 40 and Tween 80 were selected and tested to provide different hydrophilic&ndash, hydrophobic balance values and allow evaluation their solubility impact on hydrate formation and growth time. The study was performed by using a HAAKE ViscotesterTM 500 at 2 &deg, C and a surfactant concentration ranging from 0.1 wt%&ndash, 1 wt%. The solubility characteristic of the non-ionic surfactants changed the hydrate slurry in different ways with surfactants type and varying concentration. The rheological measurement suggested that oil-soluble Span surfactants was generally inhibitive to hydrate formation by extending the hydrate induction time. However, an opposite effect was observed for the Tween surfactants. On the other hand, both Span and Tween demonstrated promoting effect to accelerate hydrate growth time of cyclopentane hydrate formation. The average hydrate crystallization growth time of the blank sample was reduced by 86% and 68% by Tween and Span surfactants at 1 wt%, respectively. The findings in this study are useful to understand the rheological behavior of surfactants in hydrate slurry.

The removal of carbon dioxide (CO2) at offshore operation requires an absorption system with an environmentally friendly solvent that can operate at elevated pressure. Potassium carbonate promoted with glycine, PCGLY, is a green solvent that has potential for offshore applications. For high solvent concentrations at elevated pressure, the by-product of CO2 absorption consists of precipitates that increase operational difficulty. Therefore, this study was done to assess the CO2 absorption performance of non-precipitated PCGLY with concentration 15wt%PC+3wt%GLY, which is known to have comparable solubility performance with MDEA. A packed absorption column was used to identify the CO2 removal efficiency, mass transfer coefficient in liquid film, k l a e , and overall volumetric mass transfer coefficient, K G a v . A simplified rate-based model was used to determine k l a e and K G a v based on the experimental data with a maximum MAE value, 0.057. The results showed that liquid flow rates and liquid temperature gives significant effects on the k l a e and K G a v profile, whereas gas flow rate and operating pressure had little effect. The CO2 removal efficiency of PCGLY was found to be 77%, which was only 2% lower than 1.2 kmol/m3 MDEA. K G a v of PCGLY is comparable with MDEA. The absorption process using PCGLY shows potential in the CO2 sweetening process at offshore.

International audience; A family of metal-organic framework, [Mg3O3(CO2)3]∞ nanocrystallites which are also known as Mg-MOF-74, were synthesized by solvothermal method at high temperature under autogenous pressure. The graphene oxide was embedded into the framework via in-situ synthesis method to form a composite structure of Mg-MOF-74@nGO. n was varied from 0.1 to 0.6 wt% of the weight of pristine material. The synthesized samples were examined under Powder X-Ray Diffraction analysis to affirm their crystalline structure. Further studies were conducted by indexing the lattice parameters of the hexagonal crystals. The volume of unit cell and Scherrer’s crystallite size were also determined to study the effect of GO loading amount on their grown dimensions. The results showed that the presence of GO in the range of 0.1-0.6 wt% did not influence the dimension of the crystal except a slight expansion in vertical direction with the increment of GO loading.

A rate-based steady-state model for CO2 absorption into a PZ+AMP blended solution is presented by taking into account the column hydraulics, mass transfer resistances and chemical reactions. The simulation results were compared with the experimental results of CO2 absorption by a PZ+AMP blended solution in a packed absorption column at low and high CO2 partial pressure conditions. The model predicts CO2 concentration, amine concentration, the chemical enhancement factor, and liquid temperature profiles along the column. The model was in good agreement to predict the CO2 concentration profiles along the column at low CO2 partial pressure. However, it was found that the model needs to be corrected by introducing a correction factor for overall volumetric mass transfer coefficient (Kgae) for the simulation of CO2 concentration profiles along the column at high CO2 partial pressure conditions in the range of 404-1616 kPa.

Most of the newly discovered gas reservoir has high CO2 content (up to 70%), thus pose critical challenges to gas separation process due to the limitation of current acceptable technology. Recent report on COP-1 showed its potential as sorbent for CO2 capture due to its high adsorption capacity, low cost sorbent with good water resistance. However, scarce data on the potential of COP-1 and its selectivity for CO2/CH4 adsorbent for high pressure operation were reported. In this study, the adsorption isotherms were gravimetrically measured using magnetic suspension balance (MSB) within the range of 50–100 bar, at isothermal temperatures of 298, 318, 328 and 338 K. Langmuir and Sips isotherm models were correlated to the adsorption equilibrium data at critical and supercritical conditions. The ideal adsorption selectivities for CO2/CH4 separation were also predicted using Ideal Adsorbed Solution Theory (IAST). The ideal selectivity obtained (∼22) shows good separation performance for CO2 from CH4 onto COP-1. Furthermore, isosteric heats of adsorption calculated from Clausius-Clapeyron equation reveals that physisorption is the dominant factor for the interaction between adsorbates and surface of COP-1. Results also showed that the isostearic heat of COP-1 is a strong function of temperature and adsorbed amount. Nevertheless, the adsorption behaviour of COP-1 found in this work gives a good indication on the utilization of COP in CO2/CH4 separation for unexploited natural gas reservoir with high CO2 content.

The physical properties such as densities, viscosities, and refractive indices of aqueous solutions of potassium carbonate (PC) blended with glycine (Gly) as solvent blends for CO2 capture were measured. The properties were measured at ten different temperatures from (298.15 to 343.15) K. The mass fractions (w1 + w2) % of the (PC + Gly) blends were (0.05 + 0.01, 0.10 + 0.02, 0.15 + 0.03, 0.20 + 0.04, 0.25 + 0.05, 0.30 + 0.06, 0.35 + 0.07, and 0.40 + 0.08), respectively. The analysis of experimental results shows that, the densities, viscosities, and refractive indices of the aqueous (PC + Gly) blend increase with increasing the concentration of the potassium carbonate and glycine, and decrease with decreasing the temperature. The experimental data of density, viscosity and refractive index were correlated by a least-squares method as a function of temperature. The predicted data were estimated from coefficients of correlation equations for all measured properties, and reported with standard deviation (SD). The experimental data are in consistent with the predicted data.

The upgrading of low quality crude natural gas (NG) is attracting interest due to high demand of pipeline-grade gas in recent years. Membrane processes are commercially proven technology for the removal of impurities like carbon dioxide from NG. In this work, cross flow mathematical model has been suggested to be incorporated with ASPEN HYSYS as a user defined unit operation in order to design the membrane system for CO2/CH4 separation. The effect of operating conditions (such as feed composition and pressure) and membrane selectivity on the design parameters (methane recovery and total membrane area required for the separation) has been studied for different design configurations. These configurations include single stage (with and without recycle) and double stage membrane systems (with and without permeate or retentate recycle). It is shown that methane recovery can be improved by recycling permeate or retentate stream as well as by using double stage membrane systems. 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Although ionic liquids (ILs) hold salient features and considered as a replacement of conventional organic solvents, but their possible toxicological and ecotoxicological impacts must be considered equally in the design and development stage. Predicted no-effect concentration (PNEC) plays a vital role in assessing the ecotoxicological hazards in the ILs. A systematic methodological framework is presented for assessing the predicted environmental concentration (PEC) of ionic liquids. Initially, an effect level is predicted with a general quantitative structure–activity relationship (QSAR). Secondly, predicted no-effect concentration (PNEC) is calculated by using assessment factor (AF). The PEC is compared to the PNEC to characterize the risk for the freshwater aquatic organisms. If the ratio continued to exceed one, ionic liquids under investigation will need further aquatic risk assessment procedures, which involve iterative steps to refine the PEC and PNEC.

In this work, a series of mixed matrix membranes (MMM) were produced by incorporating zeolite-T particles into the polysulfone (PSf) membrane. Membranes obtained were characterized using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersion X-Ray (EDX) and the permeability and selectivity of CO2/CH4 of the membranes were tested. For pure polysulfone membrane, the permeability obtained were 12.33 and 4.69 for CO2 and CH4 respectively, meanwhile the CO2/CH4 ideal selectivity was 2.63. The results showed that by incorporating 4 wt% of zeolite-T into polysulfone, a highest CO2/CH4 ideal selectivity of 3.37 was obtained. Meanwhile, the highest permeability value for CO2 and CH4 of 82.3 GPU and 31.2 GPU respectively were obtained by using polysulfone membrane loaded with 3wt% of zeolite-T particles. Overall, all the resultants MMM showed higher permeability and selectivity compared to pure polysulfone membrane.

Distinct percentages of carbon molecular sieve (CMS) were added to Polyethersulfone (PES) matrix to generate mixed matrix membranes (MMMs) using solution casting method. The characterization was conducted by thermogravimetric analysis (TGA) to find out the residue solvent in the membranes and field emission scanning electron microscopy (FESEM) analysis to check the morphology of membrane. TGA results demonstrated no remaining solvent and also FESEM images demonstrated acceptable bonds between the filler particles and the polymer chains. The gas permeation results divulged that both CO 2 permeance and CO 2 /CH 4 selectivity went up with CMS loadings increment as compared to pure PES membrane. Obtained results revealed that the greatest value of CO 2 permeance (68 GPU) and CO 2 /CH 4 selectivity (11.15) at a pressure of 8 bars can be accomplished with 15 wt. % loading of CMS particles. This can be related to the kinetic diameter of CMS particles that places between CO 2 and CH 4 kinetic diameters.

Polymeric membranes demonstrate the fastest emerging field in membrane gas separation since it has huge reproducibility for large scale production and low cost fabrication. To date, many research works have emerged to propose different polymeric materials for membrane synthesis and fabrication in order to enhance gas separation performance. It has been suggested that the underlying factor that distinguishes the difference in separation efficiency among varying polymer is the amount of free volume formed throughout the polymeric matrix. Therefore, in current work, through adaptation of atomistic models by a combination of molecular dynamics and Monte Carlo or commonly known as the Cavity Energetic Sizing Algorithm (CESA), the cavity size distributions of several commonly adapted polymeric membranes for gas separation have been determined. The accuracy of the simulated molecular structure has been verified by comparing the simulated and measured experimental density. It is found from the study that that the CESA algorithm is capable of capturing the free volume distribution within the polymeric matrix, with the higher free volume polymeric membrane inheriting higher average cavity size [PTMSP (10.30A) >PPO (4.86A) >Matrimid® 5218 (4.01A) >PSF (3.25A)]. In addition, the higher free volume polymers, which exhibit shift towards the larger cavity sizes, also reveal higher gas permeability for gas molecules. The sieving capability of the polymer is also demonstrated to be correlated with the kinetic diameter of the gas penetrants as compared to the cavity size. In future work, the methodology is proposed to be employed as a preliminary step to predict polymeric membrane morphology in order to evaluate the feasibility of any polymers before being applied in gas separation.