Study on absorption and spectral properties of H2S in carboxylate protic ionic liquids with low viscosity

Solubility and Thermodynamic Parameters of H2S/CH4 in Ionic Liquids Determined by 1H NMR

Natural gas remains an important global source of energy. Usually, sour gas from the well or refinery stream contains H2S among other contaminants that should be removed to fulfill permissible standards of use. Despite the use of different gas-liquid sour gas upgrading technologies, ionic liquids (ILs) have been recognized as promising materials to remove H2S from sour gas. However, data concerned with thermodynamic solution functions of H2S in ILs have scarcely been reported in the literature. In this work, solution 1H NMR spectroscopy was employed for quantifying H2S soluble in [BMIM][Cl] and for gaining a better understanding of the H2S-IL interaction. Experiments were carried out in a Young-Tap NMR tube containing a saturated solution of H2S/CH4/[BMIM][Cl] and recording spectra from 298 to 333 K. The thermodynamic solution functions, determined from the Van't Hoff equation, showed that solubility of the H2S in the [BMIM][Cl] is an exothermic gas-liquid physisorption process (ΔsolH° = -66.13 kJmol-1) with a negative entropy change (ΔsolS° = -168.19 JK-1 mol-1). 1H NMR spectra of the H2S/[BMIM][Cl] solution show a feature of strong solute-solvent interactions. However, solubility enthalpy is a fifth of the H-S bond energy value. Results from 1H NMR spectroscopy also agree with those from the bench dynamic experiments.

Solvation Shell Anatomy of H2S and CO Dissolved in Reline and Ethaline Deep Eutectic Solvents

Rising atmospheric concentrations of anthropogenic hydrogen sulfide (H2S) and carbon monoxide (CO) as a result of industrialization have encouraged researchers to explore innovative technologies for capturing these gases. Deep eutectic solvents (DESs) are an alternative media for mitigating H2S and CO emissions. Herein, we have employed ab initio molecular dynamics simulations to investigate the structures of the nearest-neighbor solvation shells surrounding H2S and CO when they are dissolved in reline and ethaline DESs. We aim to delineate the structural arrangement responsible for favorable H2S and CO capture by analyzing the key interactions between H2S and CO solutes with various components of the DESs. We observe that in the reline-H2S system, chloride and carbonyl oxygen of urea are found to have the closest distance interaction with hydrogen atoms of the H2S solute. The sulfur atom of H2S is found to be predominantly solvated by hydrogen and oxygen atoms of urea molecules and the hydroxyl hydrogen of choline cations. The chloride ions and ethylene glycol molecules predominantly govern the solvation of H2S in the ethaline-H2S system. In both the DESs, H2S is solvated by the hydroxyl group of the choline cations rather than by their ammonium group. In the reline-CO system, all the atoms of urea along with chloride dominate the immediate solvation shell around CO. In the ethaline-CO system, hydroxyl oxygen and hydrogen atoms of ethylene glycol are found in the nearest solvation structure around CO. Both the DESs exhibit a stronger solvent-solute charge-transfer tendency toward the H2S solute compared to CO.

New Solvents for CO2 and H2S Removal from Gaseous Streams

Acid gas removal from gaseous streams such as flue gas, natural gas and biogas is mainly performed by chemical absorption with amines, but the process is highly energy intensive and can generate emissions of harmful compounds to the atmosphere. Considering the emerging interest in carbon capture, mainly associated with increasing environmental concerns, there is much current effort to develop innovative solvents able to lower the energy and environmental impact of the acid gas removal processes. To be competitive, the new blends must show a CO2 uptake capacity comparable to the one of the traditional MEA benchmark solution. In this work, a review of the state of the art of attractive solvents alternative to the traditional MEA amine blend for acid gas removal is presented. These novel solvents are classified into three main classes: biphasic blends—involving the formation of two liquid phases, water-lean solvents and green solvents. For each solvent, the peculiar features, the level of technological development and the main expected pros and cons are discussed. At the end, a summary on the most promising perspectives and on the major limitations is provided.

Measuring and Modeling the Solubility of Hydrogen Sulfide in rFeCl3/[bmim]Cl

The solubility of hydrogen sulfide in different mole ratios of ferric chloride and 1-butyl-3-methylimidazolium chloride ionic liquid (rFeCl3/[bmim]Cl, r = 0.6, 0.8, 1.0, 1.2, 1.4) at temperatures of 303.15 to 348.15 K and pressures of 100 to 1000 kPa was determined. The total solubility increased with the increase of pressure and the decrease of temperature. The solubility data were fitted using the reaction equilibrium thermodynamic model (RETM). The mean relative error between the predicted value and the measured value was less than 4%. Henry’s coefficient and the equilibrium constant of chemical reaction at each temperature were calculated. Henry’s coefficient first decreased and then increased with the increase of mole ratio, and increased with the increase of temperature. The equilibrium constant of the chemical reaction followed the same law as Henry’s coefficient. The chemical solubility was related to both Henry’s coefficient and the chemical equilibrium constant. H2S had the highest chemical solubility in FeCl3/[bmim]Cl at a mole ratio of 0.6 and a temperature of 333.15 K. The chemical solubility increased with the increase of pressure.

A high efficient absorbent for the separation of H2S from low partial pressure coke oven gas

To high efficiently remove H₂S from low partial pressure coke oven gas (COG), a novel activator (tetramethylammonium arginine, [N₁₁₁₁][Arg]) was used to blend with N-methyldiethanolamine (MDEA) for the absorption of H₂S. High concentrated [N₁₁₁₁][Arg]-MDEA aqueous solution was used as absorbent. Thermodynamic properties including absorption amount and H₂S loading values were measured, then the kinetic apparent absorption rate was calculated based on the change of absorption amount with time. The removal efficiency of H₂S in simulated COG was verified in tray towers. Compared with monoethanolamine (MEA)-MDEA and tetramethylammonium glycinate ([N₁₁₁₁][Gly])-MDEA aqueous solutions, [N₁₁₁₁][Arg]-MDEA aqueous solution takes advantages of higher absorption capacity, absorption rate and removal efficiency. Our results showed that the proposed absorbent has good industrial application prospect in coke oven gas desulfurization, because it achieved 100% removal of H₂S in the tray tower containing only 4 sieve plates under high concentrated condition (water content < 45%), which may significantly decrease the energy consumption.

Study on the Desulfurization and Regeneration Performance of Functional Deep Eutectic Solvents

Four deep eutectic solvents (DESs) were synthesized, and 5-30% polyethylenimine (PEI) was added to make functional DESs (FDESs) for dynamic absorption experiments of hydrogen sulfide. The synthesized FDESs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance. The results demonstrated the successful synthesis of FDESs. The interaction between H2S and the FDESs was discussed at a molecular level via the quantum chemical calculations. It was noticed that FDESs prefer chemisorption on H2S. In this work, the 25% PEI/FDES@EG showed the highest desulfurization performance. The effects of H2S concentration and temperature on the desulfurization performance were investigated. It was found that a relatively low temperature (30 °C) was favorable for the absorption of H2S. The 25% PEI/FDES@EG could remove H2S efficiently over a low H2S concentration. Moisture played an important role in the FDES desulfurization system. The absorption/desorption cycle experiment indicated that the FDESs retain their good regeneration performance for at least five times.