Evaluation of Organic and Ionic Liquids for Three-Phase Methanation and Biogas Purification Processes

Abstract

Three ionic liquids {butyl-trimethyl-ammonium bis(trifluoromethylsulfonyl)imide [N 1114 ][BTA], 1-methyl-1propyl-piperidinium bis(trifluoromethylsulfonyl)imide [PMPip][BTA], and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][Tf]} and two heat-transfer oils [dibenzyltoluene (DBT) and polydimethylsiloxane (trade name X-BF)] were evaluated for use in the three-phase methanation and the biogas purification processes. The density, viscosity, and surface tension of these liquids were measured and modeled as a function of the temperature. The solubilities of H 2 , CO, CO 2 , and CH 4 in these five liquids were also obtained under different pressures and temperatures. Additionally, the criteria required for each of the two processes considered were identified: the three-phase methanation process requires a thermally stable liquid with a low vapor pressure and a high H 2 , CO 2 and CO solubility, while the biogas purification process requires a highly selective CO 2 solubility liquid at ambient temperature. From the evaluation of both the experimental data and the process requirements, the most suitable liquid for each of the aforementioned processes was identified. For the three-phase methanation process, the two ionic liquids [N 1114 ][BTA] and [PMPip][BTA] and the two heat-transfer oils DBT and X-BF met the minimum requirements, while [EMIM][Tf] showed promising potential for the biogas purification process.

Global Reaction Kinetics of CO and CO2 Methanation for Dynamic Process Modeling

“…For both applications, CO methanation in polygeneration plants and CO 2 methanation of electrolysis hydrogen, a flexible (dynamic) operation of the methanation is prevalent and requires detailed process modeling and simulation in wide pressure and temperature ranges. Intensive investigations are currently carried out 1, 5, 6, 17, 18.…”

Stability studies of ionic liquid [EMIm][NTf2] under short-term thermal exposure

“…1,2 Certainly their extremely low vapour pressure may offer advantages in certain applications. 6,7 Charge transport in ionic liquids and electrochemical reactions were analysed by Watanabe 8 and Katayama. One area not yet fully explored is in the area of recycling cellulose and other organic materials or biomass pretreatment.…”

Long-term thermal stability of selected ionic liquids in nitrogen and hydrogen atmosphere

“…However, the viscosity decreases strongly with increasing temperature, whereas the temperature dependence of surface tension is relatively small [3][4][5][6][7]. The high CO 2 solubility of some ionic liquids makes them interesting for gas cleaning processes [3,[8][9][10][11]. Another important property is the low flammability [12].…”

“…However, the majority of possible applications do not require short-term but instead long-term thermal stability and therefore more reliable data for the thermal stability have to be obtained. A novel application of ionic liquids could be the use as heat transfer liquids in the three phase methanation process [3,30]. This process requires thermally stable ionic liquids in the presence of hydrogen and nickel.…”

“…1: Common cations and anions of ionic liquidsTab. 2: Comparison of some property data of two thermally stable ionic liquids with a common heat transfer oil[3,7,[19][20][21][22][23] Tab. 3: Operating conditions for TGA-experiments Sample mass in mg20 -50 Total Purge gas flow in ml/min usually 40, sometimes 100…”