Immobilization of Ionic Liquids, Types of Materials, and Applications

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High pressure solubility of methane in the ionic liquid 1-hexyl-3-methylimidazolium tricyanomethanide

In this paper, new experimental measurements of methane (CH4) solubility in the ionic liquid (IL) 1-hexyl-3-methylimidazolium tricyanomethanide ([hmim][TCM]) are presented. The solubility data were obtained using a synthetic method based on bubble-point pressure measurements for concentrations ranging from (2–10) CH4 mole% and within a temperature range of (293–363 K) and pressures up to 10 MPa. The results obtained in this work were compared with those obtained for other ILs. The IL [hmim][TCM] was found to show the lowest CH4 solubility, which is desired for application of this IL as gas sweetening solvent (low co-absorption of hydrocarbons). Moreover, the CH4 solubility was compared to the CO2 solubility in the same IL, showing that [hmim][TCM] can selectively absorb CO2 from natural gas. The experimental solubility data of CH4 in [hmim][TCM] were accurately modeled using the PR-EoS with only one temperature-independent binary interaction parameter

Separation selectivity of various gases in the ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate

The separation of carbon dioxide (CO2) from methane (CH4) is an important process in many industrial areas such as natural gas processing and biogas purification [1]. Natural gas also contains significant amounts of ethane, some propane, butane, and other higher hydrocarbons [2]. In natural gas treating, loss of heavy hydrocarbons is a concern. It is desirable to recover these compounds due to practical problems. There are many methods available for the removal of acid gases from gas streams. The most commonly used are chemical solvents, physical solvents, membranes and cryogenic fractionation [3]. Physical solvents tend to be favoured over chemical solvents when the concentration of acid gases is very high. However, if the concentration of heavy hydrocarbons is high, a physical solvent may not be the best option due to higher co-absorption of hydrocarbons. An acceptable solvent should have a high capacity for acid gas and a low capacity for hydrocarbons [4]. Therefore, ILs have been proposed to be used as a solvent for CO2 capture, because of their advantageous properties over conventional ones [5]. We found that the ionic liquid (IL) 1-ethyl-3 methylimidazoliumtris(pentafluoroethyl) trifluorophosphate ([emim][FAP]) shows the highest carbon dioxide (CO2) solubility of all ILs studied so far and shows higher selectivities for CO2/CH4 separations than any other IL, indicating the promising potential of using this IL for the separation of CO2 from natural gas. Also, the solubilities of C2H6, C3H8 and C4H10 in ([emim][FAP]) were measured and compared to the CO2 solubility in the same IL. The separation ratio between CO2 and hydrocarbons decreases as the hydrocarbon chain becomes longer. The selectivity increase accordingly to the order: SCO2/C4H10 <SCO2/C3H8 <SCO2/C2H6 <SCO2/CH4. A maximum selectivity is achieved at lower temperatures. Therefore, the CO2 removal from a natural gas stream is recommended to be performed at low temperatures in order to achieve the best separation. The obtained solubility data are modelled with the Peng-Robinson equation of state combined with quadratic mixing rule. The calculated data have been found to be in a good agreement with the experimental results

High pressure phase equilibria of binary mixtures of light hydrocarbons in the ionic liquid 1-hexyl-3-methylimidazolium tetracyanoborate

Ionic liquids have been proposed as alternative solvents for several chemical processes, including organic reactions and separations. Their well-known negligible volatility makes them perfect candidates for gas separations as no solvent losses are expected. 1-Hexyl-3-methylimidazolium tetracyanoborate ([hmim][TCB]) is a low viscosity ionic liquid with high capacity for carbon dioxide (CO2) absorption. In order to study whether the selected ionic liquid [hmim][TCB] is an appealing solvent for CO2 absorption, it is equally important that other constituents in the gas mixture will have a low absorption in [hmim][TCB]. In case we are dealing with CO2 removal from natural gas, low absorption in the ionic liquid of the light hydrocarbons like methane (CH4), ethane (C2H6) and propane (C3H8) is a prerequisite. In this paper, the solubility of CH4, C2H6 and C3 has been determined at temperatures ranging from 280 K to 370 K and pressures up to 12 MPa using a synthetic method. The CO2/CH4 selectivity has been found to be very high and a liquid–liquid partial immiscibility has been found for ethane and propane in [hmim][TCB]. The phase behavior of the system has been discusse

Selective bio-oxidation of propane to acetone using methane-oxidizing Methylomonas sp DH-1

Propane is the major component of liquefied petroleum gas (LPG). Nowadays, the use of LPG is decreasing, and thus utilization of propane as a chemical feedstock is in need of development. An efficient biological conversion of propane to acetone using a methanotrophic whole cell as the biocatalyst was proposed and investigated. A bio-oxidation pathway of propane to acetone in Methylomonas sp. DH-1 was analyzed by gene expression profiling via RNA sequencing. Propane was oxidized to 2-propanol by particulate methane monooxygenase and subsequently to acetone by methanol dehydrogenases. Methylomonas sp. DH-1 was deficient in acetone-converting enzymes and thus accumulated acetone in the absence of any enzyme inhibition. The maximum accumulation, average productivity and specific productivity of acetone were 16.62 mM, 0.678 mM/h and 0.141 mmol/g cell/h, respectively, under the optimized conditions. Our study demonstrates a novel method for the bioconversion of propane to acetone using methanotrophs under mild reaction condition