• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.212-212
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• 2006

Polyurethane wastes can be depolymerized with glycols and/or amines. The depolymerization products may be recycled for the preparation of various polyurethanes. Caprolactam was employed to depolymerize Spandex fibers and the depolymerization products were evaluated as raw materials for the preparation of polyurethane elastomers. The depolymerization products were homogeneous and could be used to prepare polyurethane elastomers acceptable for various applications as binders.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.251.2-251.2
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• 2010

Plant biomass has been proposed to be an alternative source for petroleum-based chemical compounds. Especially, phenolic chemical compounds can be obtained from lignin by chemical depolymerization processes because lignin consists of complex aromatic polymer such as trans-p-coumaryl, coniferyl and sinapyl alcohols, etc. Phenolic chemical compounds from lignin were usually produced in super critical water. However, we applied Near-critical water (NCW) system because NCW is known as a good solvent for lignin depolymerization. Organic matter like lignin can be solved in NCW system and the system has a unique acid-base property without conventional non-eco-friendly chemicals such as sulfuric acid and sodium hydroxide. In this work, we tried to optimize the NCW depolymerization system by adjusting the processing variables such as reaction time, temperature and pressure. Moreover, the amount of additional phenol was optimized by changing the molar ratio between water and phenol. Phenol was used as capping agent to prevent re-polymerization of active fragment such as formaldehyde. Alkali-lignin was used as a starting material and characterized by a Solid State 13C-NMR, FT-IR and EA (Elemental Analysis). GC-MS analysis confirmed that o-cresol, p-cresol, anisole and 4-hydroxyphathalic acid were the main product and they were quantitatively analyzed by HPLC.

• Elastomers and Composites
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• v.37 no.2
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• pp.124-133
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• 2002

Waste PBT powder was depolymerized by saponification under the mild temperature conditions($80{\sim}110^{\circ}C$) and atmospheric pressure. In depolymerization of PBT, sodium hydroxide was more effective than potassium hydroxide. The depolymerization increased with increasing reaction temperature and decreasing particle size. The reaction kinetics of depolymerization could be expressed by the shrinking unreacted core model without product layer, in which the surface reaction was a rate determining step. The activation energy was 98.1 KJ/mol. The recovery ratio of the TPA obtained from the depolymerized PBT particles of 85.1 and $105{\mu}m$ for 6 hours was about 95%.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.683-687
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• 2009

A method for depolymerization of PET by catalyzed glycolysis with an excess ethylene glycol(EG) to recover bis-hydroxyethyl terephthalate(BHET) was investigated. The product was analyzed by high-performance liquid chromatography(HPLC). Effects of operation variables such as reaction temperature, reaction time, EG/PET weight ratio were examined and kinetics of the glycolysis was studied. High temperature increases the rate of depolymerization and the yield of BHET. But, repolymerization rate was also high at too high temperature and the yield at $250^{\circ}C$ was shown to be lower than that at $230^{\circ}C$. First order reaction model was proposed to describe the glycolysis reaction. Activation energies for the reaction were obtained to be 37.8 kJ/mol above $210^{\circ}C$ and 149.6 kJ/mol below $210^{\circ}C$, which shows the glycolysis reaction is a multiple reaction. A maximum yield of BHET of 71% was achieved at a reaction temperature of $230^{\circ}C$ for 6 hr with an EG/PET weight ratio 4.

• Clean Technology
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• v.27 no.2
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• pp.190-197
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• 2021

Kraft lignin is a by-product of the pulp and paper industry, obtained as a black liquor after the extraction of cellulose from wood through the Kraft pulping process. Right now, kraft lignin is utilized as a low-grade boiler fuel to provide heat and power but can be converted into high-calorific biofuels or high-value chemicals once the efficient catalytic depolymerization process is developed. In this work, the multi-functional catalyst of Ru-Mg-Al-oxide, which contains hydrogenation metals, acid, and base sites for the effective depolymerization of kraft lignin are prepared, and its lignin depolymerization efficiency is evaluated. In order to understand the role of different active sites in the lignin depolymerization, the three different catalysts of MgO, Mg-Al-oxide, and Ru-Mg-Al-oxide were synthesized, and their lignin depolymerization activity was compared in terms of the yield and the average molecular weight of bio-oil, as well as the yield of phenolic monomers contained in the bio-oil. Among the catalysts tested, the Ru-Mg-Al-oxide catalyst exhibited the highest yield of bio-oil and phenolic monomers due to the synergy between active sites. Furthermore, in order to maximize the extent of lignin depolymerization over the Ru-Mg-Al-oxide, the effects of reaction conditions (i.e., temperature, time, and catalyst loading amount) on the lignin depolymerization were investigated. Overall, the highest bio-oil yield of 72% and the 3.5 times higher yield of phenolic monomers than that without a catalyst were successfully achieved at 350 ℃ and 10% catalyst loading after 4 h reaction time.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.875-879
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• 2008

A method for the depolymerization of polycarbonate waste by glycolysis using ethylene glycol without catalyst was explored in order to get the monomer bisphenol A (BPA). The effect of operation variables such as reaction time, reaction temperature, EG/PC weight ratio and the kinetic of glycolysis were studied. It was found that the polymerization reaction has two different activation energies depending on the reaction temperature. A drop in activation energy with temperature indicates that the reaction mechanism has shifted from one of a succession of elementary steps to another in the series. The maximum yield of BPA of 95.6% was achieved at reaction temperature $220^{\circ}C$ for 85min with EG/PC weight ratio 4.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2303-2312
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• 2018

Pretreatment process of silica-coated PET fabrics, a major low-grade PET waste, was developed using the reaction with NaOH solution. By destroying the structure of silica coating layer, impurities such as silica and pigment dyes could be removed. The removal of impurity was confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The pretreated PET fabric samples were used for depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET), by glycolysis with ethylene glycol (EG), and zinc acetate (ZnAc) catalyst. The quality of BHET was confirmed by DSC, TGA, HPLC and NMR analyses. The highest BHET yield of 89.23% was obtained from pretreated PET fabrics, while glycolysis with raw PET fabric yielded 85.43%. The BHET yield from untreated silica-coated PET fabrics was 60.39%. The pretreatment process enhances the monomer yield by the removal of impurity and also improves the quality of the monomer.

• Clean Technology
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• v.13 no.4
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• pp.251-256
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• 2007

Several studies regarding depolymerization of polycarbonate waste to get the essential monomer, bisphenol A, have been reported in recent years. However, those methods have some environmental safety problems of using highly toxic organic solvents as well as product separation problem due to the use of alkali catalyst. In this study, we proposed the combination of glycolysis and methanolysis to depolymerize the polycarbonate waste. Glycolysis reaction reached at the reaction equilibrium after about 180 minat 473.15K and dissolution of the polycarbonate was found to be a rate controlling step of the reaction. The yield of BPA was improved with the aid of combination of glycolysis and methanolysis. The methanolysis was carried out at a temperature range of $303.15K{\sim}363.15K$ and MeOH/PC molar ratio $0.5{\sim}3$. The yield of BPA had a maximum at 1.0 MeOH/PC molar ratio and increased with the reaction temperature.

• Journal of Energy Engineering
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• v.20 no.1
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• pp.36-43
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• 2011

Plant biomass has been proposed as an alternative source of petroleum-based chemical compounds. Especially, aromatic chemical compounds can be obtained from lignin by depolymerization processes because the lignin consist of complex aromatic materials. In this study, kraft lignin, the largest emitted substance among several kinds of lignin in Korea, was used as a starting material and was characterized by solid-state $^{13}C$-Muclear Magnetic Resonance($^{13}C$-NMR), Fourier Transform Infrared Spectroscopy(FT-IR), Elemental Analysis(EA). The depolymerization of kraft lignin was studied at water-phenol mixture solvent in near critical region and the experiments were conducted using a batch type reactor. The effects of water-to-phenol ratio and reaction temperature($300-400^{\circ}C$) were investigated to determine the optimum operating conditions. Additionally, the effects of formic acid as a hydrogen-donor solvent instead of $H_2$ gas were examined. The chemical species and quantities in the liquid products were analyzed using gas chromatography-mass spectroscopy(GC-MS), and solid residues(char) were analyzed using FT-IR. GC-MS analysis confirmed that the aromatic chemicals such as anisole, o-cresol(2-methylphenol), p-cresol(4-methylphenol), 2-ethylphenol, 4-ethylphenol, dibenzofuran, 3-methyl cabazole and xanthene were produced when phenol was added in the water as a co-solvent.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.886-891
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• 2008

Contact glow discharge electrolysis(CGDE) is an unconventional electrolysis where plasma is sustained by D.C. glow discharge between an electrode and the surface of electrolyte surrounding it at high voltage. In this study, the behavior of CGDE in NaCl solution and the depolymerization of fucoidan by CGDE were investigated. After onset of CGDE, increase of voltage enhanced Glow discharge which resulted in low current density and low temperature in NaCl electrolyte. From the variation of molecular weight of fucoidan with the reaction time, it was demonstrated that the degradation of fucoidan followed a first-order rate law. Molecular weight of fucoidan treated with CGDE was about 40 times lower compared to initial fucoidan without content decrease of sulfate and fucos.