Phase-change solvents exhibit the promising potential to reduce the regeneration energy for CO 2 capture. In this paper, 3-dimethylaminopropylamine (DMAPA) with intramolecular primary and tertiary amino groups was mixed with solvent NHD and water for phase-change absorption of CO 2 in the model flue gas. The results show that the homogeneous mixture changes into two phases after CO 2 absorption when NHD/H 2 O ranges from 9:1 to 5:5 and 90% of CO 2 is enriched in the lower phase with only 23% of the total volume. The absorption loading reaches 1.06 mol CO 2 /mol amine, the phase separation time for DMAPA−NHD−H 2 O is only 14% of that for MEA−SA−H 2 O, and the viscosity of the lower phase is only 37.14 mPa•s when DMAPA and NHD/H 2 O are 1 M and 8:2, respectively. Analysis of the reaction mechanism shows that the primary amino group of DMAPA initially reacts with CO 2 and the tertiary amino group captures proton of zwitterionic intermediate as an acceptor. The mixed-amine effect is suggested to explain the high absorption performance of the DMAPA−NHD−H 2 O mixture. The energy estimation shows that the regeneration energy is reduced by 42% compared with that of the 5 M MEA solution, which confirms the advantage of phase-change absorption using DMAPA−NHD−H 2 O.

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Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Fourier transform infrared (FTIR) spectroscopy. The results show that the gas temperature before precursor gases entering the glow-discharge zone remarkably influences the hydrogen bonding configurations and the hydrogen content in a-Si:H thin films. The hydrogen content decreases from 18% down to 11% when increasing the gas temperature from room temperature (RT) to 433 K. Meanwhile, the clustered hydrogen at the physical film surface or at the internal surfaces of the microvoids decreases, indicating that a-Si:H thin films are densified at higher precursor gas temperatures. For a-Si:H thin films deposited at gas temperature of 433 K, the isolated silicon-hydrogen bonding configuration is predominant in the testing films. a-Si:H thin film, gas temperature, hydrogen bonding, FTIR, PECVD Citation: Wu M Y, Li W, Qiu Y J, et al. Hydrogen bonding in hydrogenated amorphous silicon thin films prepared at different precursor gas temperatures with undiluted silane.

Biphasic solvent 3-dimethylaminopropylamine (DMAPA)/poly(ethylene glycol) dimethyl ether (NHD)/H2O solution is a promising absorbent for CO2 capture. The kinetics of CO2 absorption in both DMAPA/NHD/H2O system and DMAPA/H2O systems was investigated and compared in a wetted wall column reactor with different CO2 loadings at different CO2 partial pressures from 30 to 70 °C. The equilibrium CO2 loadings were also determined. Meanwhile, the density and viscosity for both systems were measured. In both systems, the mass transfer flux of CO2 increases linearly with the increase of CO2 partial pressure. The kinetic data were interpreted by the zwitterion mechanism. The overall mass transfer constant was determined according to the absorption rate experiments performed in the pseudo-first-order regime. The overall mass transfer resistances increase with the increase of CO2 loading and decrease with the increase of temperature. The addition of NHD decreases the equilibrium CO2 loadings at the same CO2 partial pressure and temperature. However, it increases the enhancement factor significantly and can promote both the absorption and the desorption process. It provides basic information not only for the further utilization of DMAPA/NHD/H2O solution, which is helpful for the design of absorption reactor, but also for developing new phase-change absorbents for CO2 capture.

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