Hyun-Tae Jang

Novel microporous hypercross-linked conjugated quinonoid chromophores with broad light absorption and CO2 sorption characteristics

We have discovered formation of hypercross-linked conjugated quinonoid chromophores (polymers) with broad light absorption characteristics during cross-linking of aromatic monomers, such as benzene, naphthalene, anthracene, phenanthrene and 1,3,5-trimethyl benzene with 1,3,5-trioxane in the presence of an FeCl3 catalyst. The para or ortho –CH2 groups that bridge aromatic monomers were dehydrogenated during polymerization to form the quinonoids. The quinonoid chromophores were confirmed by their DRS-UV Vis and FTIR spectra. We have also discovered similar such quinonoid chromophores in the hypercross-linked polymers of aromatic monomers, reported from 1970 onwards by different research groups. The polymers were synthesized by similar experiments with an FeCl3 catalyst, and brown colored. As all the polymers bear low band gaps, they strongly absorb light covering the wavelength range of 1000 to 200 nm. Most of the hypercross-linked polymer matrices carry microporous spheres of about 1 to 5 μm diameter and showed 6–7% CO2 sorption. The polymers with their low band gaps will inspire research on semiconductors, solar cell devices, UV stabilizers/absorbers and infrared absorbers/detectors, molecular sensors and academic study.

A new strategy to synthesize hypercross-linked conjugated polystyrene and its application towards CO2 sorption

Polystyrene is cross-linked to generate micropores for sorption applications. Herein, we report, hypercross-linking of polystyrene in the presence of Friedel-Crafts catalyst, FeCl3 without a cross-linker. For comparison, polystyrene was also hypercross-linked with a cross-linker, dimethoxy methane with the same catalyst. The cross-linking and de-hydrogenation of cross-links to quinonoid formation were confirmed by FT-IR and 13C-NMR techniques. The hyper cross-linked polymers (HCPs) were also characterized by TGA, DRS-UV, SEM, Raman, BET and CO2 sorption techniques. All the HCPs showed a maximum of 5 weight % CO2 sorption at 25 oC and 1 atm. The same polymers could also be applied for the sorption of other air pollutants.

Microporous Hypercross-linked Conjugated Quinonoid Chromophores of Anthracene: Novel Polymers for CO 2 Adsorption

Microporous hypercross-linked conjugated quinonoid chromophores represent a novel class of amorphous polymers, synthesized by the reaction of anthracene with dimethoxy methane in the presence of FeCl3 catalyst. Their N2 adsorption isotherms confirm their microporous nature. Diffuse reflectance UV-Visible (DRS UV-Vis) spectroscopy confirms their matrix built with the conjugated quinonoids by their broad light absorption characteristics extending from 1000 nm to 200 nm with the absorbance maximum close to 400 nm. The catalyst cross-linked anthracene with -CH2- bridges and subsequently dehydrogenating them to form quinonoids. Their Fourier transform infrared (FTIR) spectra showed their characteristic quinonoid vibrations between 1600 and 1700 cm−1. The synthesis of polymers was carried out at 30, 40, 50, 60, 70 and 80 °C, but the quinonoid content of the polymer obtained at 80 °C was higher than that of the others. Their scanning electron microscopy (SEM) images showed microspheres of 1 to 5 μm size built with tiny particles. Their surfaces were not smooth. The polymer synthesized at 80 °C showed 5.1 wt% CO2 sorption at 25 °C and 0.1 MPa, but when it was recross-linked, the CO2 sorption increased to 8 wt%. Hence, hypercross-linked conjugated quinonoid chromophores of anthracene are good for sorption of CO2.

Adsorption/Desorption Properties of ACF on Toluene and MEK with Operation Condition

Adsorption/desorption characteristics of low concentration methylethylketone(MEK) and toluene vapors in beds packed with activated carbon fibers(ACF) was investigated. Performance of ACF adsorption was characterized by the equilibrium capacity, time to reach equilibrium and desorption efficiency. Experiments were carried out to define the effect of operation variables, such as feed concentration, flow rate, moisture content and bed height. The breakthrough time was shorten with the increase of temperature, flow rate and feed concentration. In addition, an increase of packed height of adsorbents lengthen the breakthrough time. The ACF loaded with MEK and toluene was satisfactorily regenerated by programed heating. It is observed that MEK is more easily removed than toluene at below temperature of 150℃.

Adsorption and antibacterial property of impregnated activated carbon fiber

To introduce the antibacterial activity, ACF(activated carbon fiber) was impregnated by nano-sized Ag, Mn, and phosphoric acid. It was observed by the SEM analysis that Ag, Mn and phosphoric acid were properly impregnated at the ACF. The impregnated ACF showed lower adsorption performance than the pure ACF. It is found that ACFs impregnated by nano-sized Ag or phosphoric acid have a good antibacterial activity against bacillus cereus and salmonella entaritidis. but in the case of ACF impregnated with Mn, it have not any antibacterial effect on the bacillus cereus and salmonella entaritidis.

Thermal Decompostion of Methane Using Catalyst in a Fluidized Bed Reactor

In this paper, Thermocatalytic decomposition of methane in a fluidized bed reactor (FBR) was studied. The technical approach is based on a single-step decomposition of methane over carbon catalyst in air/water vapor free environment. The factors affecting methane decompostion catalyst activity in methane decomposition reactions were examined. The fluidization phenomena in a gas-fluidized bed of catalyst was determined by the analysis of pressure fluctuation properties, and the results were confirmed with characteristics of methane decomposition. The effect of parameters on the H2 yield was examined for methane decompostion. The decompstion rate was affected by the fluidization quality such as mobility, U-Umf, carbon attrition, elutriation and effectiveness density of fluidization gas.

Characteristics of low temperature pyrolysis and liquid product distribution of ABS plastics

Characteristics of pyrolysis and liquid product distribution of ABS plastics have been studied in the thermogravimetric(TG) reactor and bomb microreactor. Pyrolysis reactions were performed at temperature and yield of each pyrolytic product was obtained by the weight measurement method. The molecular weight distributions of liquid products were determined by the GC-SIMDIS method. It was observed that solid residue which could not be detected in the thermogravimetric experiments was significantly formed in the batch-type microreactor. It was found that the yield and average molecular weight of liquid products were decreased with the increase of reaction temperature and time. but the formation of styrene monomer was significantly increased. The chain-end scission rate parameters were determined to be 54.1kcal/mole far ABS by the Arrhenius plot.