The objective of the present study is to develop a new type of “molecular basket” sorbent (MBS) by using inexpensive and commercially available carbon materials instead of mesoporous silica molecular sieves as supports for CO2 capture from flue gas. Several commercial carbon materials, including activated carbons and carbon blacks, with different pore sizes and pore volumes have been used to prepare the carbon-based MBS (CB-MBS) by loading the CO2-philic polyethylenimine (PEI) on them. The CO2 sorption performance of the prepared CB-MBS was evaluated by using a thermogravimetric analyzer and a fixed-bed flow sorption system. Effects of the pore properties of the carbon supports, PEI loading amount, sorption temperature, and moisture on the sorption capacity were examined. A sorption capacity of 135 mg-CO2/g-sorb was obtained by loading 50 wt % PEI on a carbon black, which is almost the same as that of PEI(50)/SBA-15 prepared by loading 50 wt % PEI on SBA-15. The higher CO2 sorption capacity of 154 mg-CO2/g-sorb was achieved when increasing the PEI loading on the carbon black to 65 wt %. Characterization of the porous structure of the carbon materials indicates that the high sorption capacity of the carbon-black-supported PEI sorbents can be ascribed to their high pore volume and large pore size. It was further found that the volume-based capacity of PEI(50)/C4 was even higher than that of PEI(50)/SBA-15 by 57% due to the higher packing density (0.35 g/mL) of the former than that (0.22 g/mL) of the latter. Because of its high CO2 sorption performance and low preparation cost, the carbon-based MBS could be a promising sorbent for cost-efficient CO2 capture from flue gas.

In order to reduce the sorbent preparation cost and improve its volume‐based sorption capacity, the use of an inexpensive and commercially available silica gel was explored as a support to prepare a solid polyethylenimine sorbent (PEI/SG) for CO2 capture from flue gas. The effects of the pore volume and particle size of the silica gels, molecular weight of polyethylenimine and amount of polyethylenimine loaded, sorption temperature and moisture in the flue gas on the CO2 sorption capacity of PEI/SG were examined. The sorption performance of the developed PEI/SG was evaluated by using a thermogravimetric analyzer and a fixed‐bed flow sorption system in comparison with the SBA‐15‐supported polyethylenimine sorbent (PEI/SBA‐15). The best PEI/SG sorbent showed a mass‐based CO2 sorption capacity of 138 mg‐CO2/g‐sorbent, which is almost the same as that of PEI/SBA‐15. In addition, the PEI/SG gave a high volume‐based sorption capacity of 83 mg‐CO2/cm3‐sorbent, which is higher than that of PEI/SBA‐15 by a factor of 2.6. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2495–2502, 2012

Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EAR-LINET)

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The continuous rise of the atmospheric CO 2 concentration and its linkage with climate change demand an urgent technological solution to reduce CO 2 emissions. 1 Carbon capture and sequestration (CCS) have been considered as one of the key options for mitigating CO 2 emissions. 2 On the basis of the current technology (amine scrubbing), the CCS cost is very high, in which the CO 2 capture from the sources was estimated to be two-thirds or even more of the total costs for CCS. 3,4 Consequently, many research approaches have been carried out for the development of novel technologies to reduce the cost for the CO 2 capture. Among all of these research efforts, the CO 2 capture by adsorption/sorption on the immobilized amine sorbents has been considered as one of the most promising approaches. [4][5][6][7][8][9] In our previous studies for CO 2 capture, we have developed the novel sorbents, called as the "molecular basket" sorbents (MBSs), which were prepared by immobilizing CO 2 -philic polyethylenimine (PEI) on silica mesoporous molecular sieves. [10][11][12] The second generation of MBS (MBS-2) prepared by loading 50 wt % PEI on SBA-15 showed a CO 2 capacity as high as 140 mg of CO 2 /g of sorbent at a CO 2 partial pressure of 15 kPa, because the MBS increases the total density of the accessible amine functional groups on/ in the sorbent. [13][14][15] In addition, the MBS has also some other significant potential advantages, including high selectivity for CO 2 , no or less corrosion problem, high sorption/desorption rate because of high gas-sorbent interface area (∼80 m 2 /g), positive effect of moisture on the MBS performance, and lower energy consumption during regeneration. However, the support materials currently used in the preparation of the

Stable electrical doping of organic semiconductors is fundamental for the functionality of high performance devices. It is known that dopants can be subjected to strong diffusion in certain organic semiconductors. This work studies the impact of operating conditions on thin films of the polymer poly(3-hexylthiophene) (P3HT) and the small molecule Spiro-MeOTAD, doped with two differently sized p-type dopants. The negatively charged dopants can drift upon application of an electric field in thin films of doped P3HT over surprisingly large distances. This drift is not observed in the small molecule Spiro-MeOTAD. Upon the dopants' directional movement in P3HT, a dedoped region forms at the negatively biased electrode, increasing the overall resistance of the thin film. In addition to electrical measurements, optical microscopy, spatially resolved infrared spectroscopy, and scanning Kelvin probe microscopy are used to investigate the drift of dopants. Dopant mobilities of 10 to 10 cm V s are estimated. This drift over several micrometers is reversible and can be controlled. Furthermore, this study presents a novel memory device to illustrate the applicability of this effect. The results emphasize the importance of dynamic processes under operating conditions that must be considered even for single doped layers.

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Polyallylamine (PAA)-based molecular basket sorbents (MBS) have been studied for CO capture in comparison with polyethylenimine (PEI)-based MBS. The characterizations including N physisorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermogravimetric analysis (TGA) showed that PAA (M =15 000) is more rigid and has more steric hindrance inside SBA-15 pores than PEI owing mainly to its different polymer structure. The effects of temperature and PAA loading on the CO sorption capacity of PAA-based MBS have been examined by TGA by using 100 % CO gas stream and compared with PEI/SBA-15. It was found that the capacity of the PAA/SBA-15 sorbent increased with increasing temperature. The optimum capacity of 88 mg g was obtained at 140 °C for PAA(50)/SBA-15 whereas the optimum sorption temperature was 75 and 90 °C for PEI-I(50)/SBA-15 (PEI-I, M =423) and PEI-II(50)/SBA-15 (PEI-II, M =25 000), respectively. The capacity initially increased with the increase of PAA loading and then dropped at high amine contents, owing to the increased diffusion barrier. The highest CO capacity of 109 mg g was obtained at a PAA loading of 65 wt %, whereas the PAA(50)/SBA-15 sorbent gave the best amine efficiency of 0.23 mol mol . The effect of moisture was examined in a fixed-bed flow system with simulated flue gas containing 15 % CO and 4.5 % O in N . It was found that the presence of moisture significantly enhanced CO sorption over PAA(50)/SBA-15 and greatly improved its cyclic stability and regenerability. Compared with PEI/SBA-15, PAA/SBA-15 possesses a better thermal stability and higher resistance to oxidative degradation. However, the CO sorption rate over the PAA(50)/SBA-15 sorbent was much slower.