Stable Absorption Performance Research Articles

Capturing CO2 into the precipitate of a phase-changing solvent after absorption.

The major drawback of aqueous alkanolamine-based CO2 capture processes is the high energy penalty for regeneration. To overcome this weakness, we studied the absorption of CO2 with amines dissolved in nonaqueous solvents. It was observed that triethylenetetramine (TETA) dissolved in ethanol produces a solid precipitate after absorption, which can then be easily separated and regenerated. As a comparison, a TETA/water solution does not form any precipitate after absorbing CO2. The TETA/ethanol solution offers several advantages for CO2 capture in absorption rate, absorption capacity, and absorbent regenerability. Both the rate and capacity of CO2 absorption with the TETA/ethanol solution were significantly higher than with a TETA/water solution, because ethanol not only promotes the solubility of CO2 in the liquid phase but also facilitates the chemical reaction between TETA and CO2. This approach was able to capture 81.8% of the absorbed CO2 in the solid phase as TETA-carbamate. In addition, results show that the decomposition of TETA-carbamate can be completed at 90 °C. Moreover, the cycling absorption/regeneration runs of the TETA/ethanol solution display a relatively stable absorption performance.

Efficient and reversible capture of SO2 by pyridinium-based ionic liquids

A series of thermally stable pyridinium-based ionic liquids (ILs), including [C4Py][BF4], [C6Py][BF4], [C8Py][BF4], [(C4MPy)-M-3][BF4], [(C6MPy)-M-3][BF4], [(C8MPy)-M-3][BF4], [C4Py][SCN] and [C4Py][Tf2N], were firstly applied as new absorbents for SO2 capture. It was found that among the investigated ILs [C4Py][SCN] has the highest absorption capacity of 0.841 gSO(2) gIL(-1) under ambient conditions, which is much higher than that of the most reported imidazolium-based ILs. The selectivity for SO2/CO2, SO2/N-2 and SO2/O-2 was also studied and the higher selectivity for SO2 to other gases using the [C4Py][SCN] was achieved. Moreover, how the water content affects the absorption capacity of SO2 was further investigated. The absorption mechanism was studied using Fr-IR and NMR spectroscopy, as well as Quantum Chemical calculation and Molecular Dynamic (MD) simulation. It was demonstrated that the physical absorption occurs in pyridinium-based ILs for SO2 capture. Comparing with cation of IL, anion plays a dominant role in SO2 absorption, which was proved both by the interaction enthalpy of IL-SO2 using Quantum Chemical calculation and the experimental results. MD simulation results further confirmed that the higher absorption capacity of SO2 in [C4Py][SCN] is mostly attributed to the stronger electrostatic interaction between the anion and SO2. In addition, the [C4Py][SCN] can still keep the stable absorption performance after five cycles of absorption and desorption, implying the pyridinium-based us show great potentials as cost effective and green absorbents for SO2 capture applications. (C) 2014 Elsevier B.V. All rights reserved.