Il-Hyun Baek

Highly selective thin film composite hollow fiber membranes for mixed vapor/gas separation

In the present study, thin film composite membranes have been prepared using an interfacial polymerization method. First, we coated a polydopamine (PDA) layer using different concentrations of PDA solution on polyethersulfone (PES) hollow fiber supports. After the PDA coating layer, thin film composite (TFC) membranes were prepared with 3,5-diaminobenzoic acid (3,5-DABA) as an aqueous phase monomer and trimesoyl chloride (TMC) as an organic phase monomer to synthesize a hydrophilic polyamide layer. This prepared selective layer is considered desirable to fabricate hydrophilic TFC membranes for water vapor/N2 separation. The TFC membranes by interfacial polymerization were confirmed and discussed using the accumulated results of characterization. Hollow fiber membranes (HFM) surface modification with PDA before TFC coatings was proposed to modestly and effectively enhance the membrane selectivity. The newly prepared TFC hollow fiber membranes acquired reasonably excellent selectivity and superior permeation fluxes. As a result, membrane sample MS4 coated with 2.0 wt% PDA and TFC prepared using 0.5 wt% of 3,5-DABA with 0.2 wt% of TMC and 60 s of reaction time showed the best permeance and selectivity as 3185 GPU and 195, respectively, compared with other TFC membranes prepared with different PDA concentrations. Overall, the membranes showed good performance in the entire range of operating conditions investigated.

Modelling and analysis of pre-combustion CO2 capture with membranes

A pre-combustion CO2 capture system was modelled with three different membranes. It comprised an amine absorber for the elimination of H2S, high- and low-temperature water gas shift reactors for the conversion of CO to CO2 and a membrane to keep over 90% of the CO2 in the retentate. The absorber and equilibrium reactors were modelled using rigorous models, while the partial least squares model was used for three different types of membranes to predict the experimental results. The effectiveness of the modelling of the reactors and membranes was tested through comparison of simulated results with experimental data. The effects of operating pressure and membrane type are also discussed, and it was found that using a smaller membrane under high pressure lowered the membrane’s cost but also lowered energy recovery.

Adsorptive separation of carbon dioxide by polyethyleneimine modified adsorbents

Utilization of carbon dioxide (CO2) has become an important global issue due to significant and continuous rise in atmospheric CO2 concentrations. To find a potential solution, two types of mesoporous materials, MCM-41 and MCM-48, were synthesized and impregnated with 30, 50 and 70 wt% of polyethyleneimine (PEI) in methanol to evaluate the performance of the materials in terms of CO2 adsorption. The materials were characterized by XRD, TGA, FTIR, TEM, SEM, N2-physisorption and BET techniques. All the PEI-loaded materials exhibited substantially higher reversible CO2 adsorption-desorption behaviors with >99% recovery. The above study proved that MCM-48 is a better material as compared to MCM-41 for loading of PEI. The material with 50 wt% loading of PEI on MCM-48, showed maximum adsorption of 248 mg/g-PEI at 80 °C which is about 30 times higher than that of MCM-48 and about 2.3 times that of pure PEI.

Preparation of semi-activated carbon fibers

Preparation of semi-activated carbon fibers (SACFs) using a precursor consisting of coal tar pitch and phenolic resin coated on glass fiber was investigated. Stabilization of the fiber structure by crosslinking both the phenolic resin and coal tar pitch was essential to achieving high surface areas during high temperature activation. The phenolic resin was cured by using aqueous catalyst (hydrochloric acid/formaldehyde) followed by oxidative stabilization of the pitch. A surface area of 1,206 m2/g based on the precursor was obtained through activation using carbon dioxide/steam at 880 ‡C. The pore size distribution was shown to be vary narrow using the Horvath-Kawazoe (HK) method.

Catalytic reactivity of an iridium complex with a proton responsive N-donor ligand in CO2 hydrogenation to formate

Catalytic hydrogenation of CO2 into formic acid/formate is an attractive conversion in the utilization of CO2. Although various catalysts with high catalytic efficiency are reported, a very few studies have been carried out to correlate/understand the efficacy and stability of the hydrogenation catalysts, which could be helpful to direct the future design strategy of corresponding catalysts. Herein, a half-sandwich iridium complex containing bibenzimidazole as a proton responsive N-donor ligand, [Cp*Ir(BiBzImH2)Cl]Cl, has been synthesized and fully characterized. The generation of an N− anion by the deprotonation of a bibenzimidazole group resulted in a significant enhancement of activity. The Ir complex showed about 20 times higher catalytic efficiency in the hydrogenation of CO2 into formate than that of its bipyridine counterpart [Cp*Ir(Bpy)Cl]Cl. The time dependent catalytic activity studies revealed that the initial excellent activity of [Cp*Ir(BiBzImH2)Cl]Cl was reduced when catalytic cycle proceeds; which was found to be the structural instability of the catalyst caused by steric hindrance between the bibenzimidazole and Cp* ligands.

Carbon dioxide absorption characteristics according to amine mixtures with different order

Abstract The advanced absorbent that used amine mixture with different order were developed to separate carbon dioxide emitted from fossil fuel power plant. The carbon dioxide absorption capacity for mixtures with different amine(primary, secondary and tertiary) were investigated according to CO 2 partial pressure. The carbon dioxide absorption capacity at the same pressure is ordered as 3DMA1P 30wt%>3DMA1P 27wt%+MEA 3wt%>3DMA1P 27wt%+DEA 3wt%. The result indicates that mixing tertiary amine with primary amine yields more efficient carbon dioxide absorbent than mixing tertiary with secondary amine does. Finally, the predicted semi-empirical gas-liquid equilibrium model fitted with experimental results. Key Words : Absorbent, Amine, Carbon dioxide, Separation 본 논문은 2013년도 정부(미래창조과학부)의 재원으로 (재)한국이산화탄소포집 및 처리연구개발센터의 지원을 받아 수행된 연구임 (지원과제번호:2011-0031969) * Corresponding Author : So-Jin Park(Chungnam Univ.)Tel: +82-42-821-5684 email: sjpark@cnu.ac.kr Received August 10, 2013 Revised September 4, 2013 Accepted September 6, 2013

Degradation Characteristics of Aqueous MEA Solution by Corrosion Products and Absorption Conditions

>> The absorbent loss due to degradation in CO2 capture process using aqueous alkanol amine solution has adverse effect on the economics of overall process. The degradation causes absorbent loss, equipment corrosion, foaming, adhesive material producing and viscosity increase in operation. In this study, the degradation characteristics of CO2 capture process using MEA (monoehtanolamine) under various conditions such as O2 partial pressure, CO2 loading and absorbent temperature. The effects of iron, which generated from the equipment corrosion, on absorbent degradation were studied using Fe2SO4 containing MEA solution. The produced gases were analyzed by FT-IR(Fourier Transform Infrared Spectrophotometer) and the specifically measured NH3 concentration was used as a degradation degree of aqueous MEA solution. The experiments showed that the higher CO2 loadings (α), O2 fraction (yO2) and reaction temperature enhanced the more degradation of aqueous MEA solution. Comparing other operation parameters, the reaction temperature most affected on the degradation. Therefore, it could be concluded that the above parameters affects on degradation should be considered for the selections of CO2 absorbent and operating conditions.

Characteristics of Water Gas Shift and Membrane Process for Pre-combustion CO 2 Capture

Global warming due to greenhouse gas emissions is considered as a major problem worldwide, and many countries are making great efforts to reduce carbon dioxide emissions. Many technologies in post-combustion, pre-combustion and oxy-fuel combustion capture have been developed. Among them, a hybrid pre-combustion capture system of a water gas shift (WGS) reactor and a membrane gas separation unit was investigated. The 2 stage WGS reactor integrated high temperature shift (HTS) with a low temperature shift (LTS) was used to obtain a higher CO conversion rate. A Pd/Cu dense metal membrane was used to separate from selectively. The performance of the hybrid system in terms of CO conversion and separation was evaluated using a 65% CO, 30 % and 5% gas mixture for applications to pre-combustion capture. The experiments were carried out over the range of WGS temperatures (), WGS pressures (0-20bar), Steam/Carbon (S/C) ratios (2.5-5) in a feed gas flow rate of 1 L/min. A very high CO conversion rate of 99.5% was achieved with the HTS-LTS 2 stage water gas shift reactor, and 83% was concentrated in the retentate using the Pd/Cu membrane.