Young Soo Ko

Epoxide-functionalization of polyethyleneimine for synthesis of stable carbon dioxide adsorbent in temperature swing adsorption.

Amine-containing adsorbents have been extensively investigated for post-combustion carbon dioxide capture due to their ability to chemisorb low-concentration carbon dioxide from a wet flue gas. However, earlier studies have focused primarily on the carbon dioxide uptake of adsorbents, and have not demonstrated effective adsorbent regeneration and long-term stability under such conditions. Here, we report the versatile and scalable synthesis of a functionalized-polyethyleneimine (PEI)/silica adsorbent which simultaneously exhibits a large working capacity (2.2 mmol g−1) and long-term stability in a practical temperature swing adsorption process (regeneration under 100% carbon dioxide at 120 °C), enabling the separation of concentrated carbon dioxide. We demonstrate that the functionalization of PEI with 1,2-epoxybutane reduces the heat of adsorption and facilitates carbon dioxide desorption (>99%) during regeneration compared with unmodified PEI (76%). Moreover, the functionalization significantly improves long-term adsorbent stability over repeated temperature swing adsorption cycles due to the suppression of urea formation and oxidative amine degradation.

Synthesis, X-ray structures, and controlled ring opening polymerization behavior of L-lactide using titanium complexes chelated by tetradentate diamine-diethanolate ligand.

The synthesis and characterization of LTi(O-i-Pr)(2) (1) and LTiCl(2) (2) complexes containing a new [ONNO]-type tetradentate diamine-diethanolate ligand such as (HOCMe(2)CH(2)NMeCH(2)CH(2)NMeCH(2)CMe(2)OH) (LH(2)) was achieved. Single-crystal X-ray analyses revealed that monomeric complexes 1 and 2 had pseudo-C(2) and pseudo-C(1) symmetric distorted octahedral geometry, respectively. Interestingly, complex 1 has fac-fac geometry for tetradentate L around a Ti centre in both solid and solution, whereas complex 2 has different geometry in solid (mer-fac, C(1)) and solution (fac-fac, C(2)). They are effective catalysts for the controlled ring opening polymerization of L-lactide, as shown by the linearity of the number average of the molecular weight of polylactides versus conversion, as well as narrow PDI values.

FT-IR study on CO2 adsorbed species of CO2 sorbents

The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO2/N2, dry CO2/air with varying concentration, and humid CO2/air mixtures to demonstrate the effect of the gas conditions on the CO2 adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO2 sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO2. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO2 concentration can affect the CO2 sorption capacity as well as the extent of degradation of sorbents.

Chemical compositional distribution of ethylene-1-butene copolymer prepared with heterogeneous ziegler-natta catalyst: TREF and crystaf analysis

Ethylene-1-butene copolymers were prepared with SiO2-supported TiCl4 catalyst by changing of 1-butene/ethylene molar ratio in feed, and the resulting copolymers were analyzed using temperature rising elution fractionation (TREF) and crystallization fractionation (Crystaf) methods to investigate the influence of C4/C2 molar ratio in feed on chemical compositional distribution and other parameters such as molecular weight and its distribution. TREF analysis showed that the copolymers had a broad and bimodal chemical compositional distribution (CCD) regardless of the content of 1-butene in the copolymer. The chemical composition was in the range of 5 to 55 branches per 1,000 carbons for all copolymers prepared in the study. Furthermore, the broader CCD was revealed for the copolymers having the higher content of 1-butene. Crystaf analysis did not showed a bimodal CCD for the copolymers having the 1-butene content of less than 5.1 wt%. The lower crystalline part having higher 1-butene content in Crystaf analysis was less than that of TREF analysis.

Synthesis of Ti(dibenzoylmethane)₂(O-i-Pr)₂ and its L-Lactide Ring-Opening Polymerization

Ti(dbm)2(O-i-Pr)2 catalyst was synthesized using Ti(O-i-Pr)4 and dibenzoylmethane(dbm) to develop a catalyst for the polymerization of L-lactide. The L-lactide polymerization behaviors of Ti(dbm)2(O-i-Pr)2 catalyst was observed with varying molar ratio of L-lactide/catalyst and polymerization time. The conversion and molecular weight increased with increasing L-lactide/catalyst molar ratio. Ti(dbm)2(O-i-Pr)2 catalyst was found to have a low catalytic activity because of the presence of a phenyl group in the catalyst and interfering with the lactide insertion during the polymerization reaction. Benzyl alcohol as an initiator resulted in a significant reduction in conversion of Ti(dbm)2(O-i-Pr)2 catalyst. The molecular weight of the obtained polymer was measured by DSC and GPC, and the molecular structure of PLA was confirmed by H NMR.

Preparation of PEDOT-ordered mesoporous carbon hybrid material using vapor phase polymerization

A hybrid composite was prepared by the formation of poly (3,4-ethylenedioxythiophene) (PEDOT) layer on two types of ordered mesoporous carbon (OMC) by vapor phase polymerization. The morphology, chemical composition, pore structure, and electrical properties of the normal type ordered mesoporous carbon (NTOMC) and rod type ordered mesoporous carbon (RTOMC) composites were compared and analyzed. The surface morphology of the PEDOT-OMC composite did not change, due to the uniform coating of PEDOT layer on the OMC. The content of PEDOT in the composite and the thickness of the coating layer both increased with the amount of the oxidizing agent, Iron (III) p-toluenesulfonate (FTS) used in VPP. Pore size, porosity, and surface area of PEDOT-OMC composite decreased with coating of PEDOT layer on the outer surface of the OMC, and the mesopore inner wall. Electrical resistance decreased with an increase in the thickness of the PEDOT layer coated on the OMC. The PEDOT-RTOMC composite had lower electrical resistivity than the PEDOT-NTOMC composite, suggesting that rod-type morphology is advantageous for electron transport. The capacitance was also higher for the PEDOT-RTOMC than for the PEDOTNTOMC, which is thought to be proportional to the surface area of the composite determined by the external and internal structure of the material.

In-Situ Immobilization of Ni Complex on Amine-Grafted SiO2 for Ethylene Polymerization

The results on the In-Situ synthesis of Ni complex on amine-grafted SiO2 and its ethylene polymerization were explained. SiO2/2NS/(DME)NiBr2 and SiO2/3NS/(DME)NiBr2(Ni(II) bromide ethylene glycol dimethyl ether) catalysts were active for ethylene polymerization. The highest activity was shown at the polymerization temperature of 25 °C, and SiO2/2NS/(DME)NiBr2 exhibited higher activity than SiO2/3NS/(DME)NiBr2. The PDI values of SiO2/2NS/(DME)NiBr2 were in the range of 8~18. The aminosilane compounds and Ni were evenly grafted and distributed in the silica. It was proposed that DME ligand was mostly removed during the supporting process, and only NiBr2 was complexed with the amine group of 2NS based on the results of FT-IR and ethylene polymerization.

Improvement of Mechanical Properties of Waterborne Polyurethane Thin Film Prepared Using Bio-polyol Derived from Cashew Nut Shell Oil (CNSL)

Cashew nut shell liquid oil (CNSL), a vegetable oil, is a renewable and eco-friendly resource that can replace a raw materials for preparing petroleum-derived polyols. In this study, difunctional diglycidyl ether from cardanol of CNSL was modified by ring opening reaction with various second amine compounds in order to prepare multi-functional CNSL based polyols having 3, 4, and 6 of hydroxyl groups. Regarding environmental issue of organic solvent based conventional polyurethane, waterborne polyurethane (PUD) was synthesized by mixed polyol prepared with various ratios using CNSL based polyols with ether and/or siloxane based polyols. Chemical structure of the synthesized CNSL based polyols, PUD and improvement of mechanical and physicochemical thermal properties were confirmed. It might be due to effect of organic-inorganic hybridization from adding Si-O-Si bond to main chain of PUD and increase of crosslinking density from increasing hydroxyl groups of the multi-functional CNSL based polyol.