Depolymerization of Kraft Lignin at Water-Phenol Mixture Solvent in Near Critical Region

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.

물-페놀 혼합 용매의 근임계 하에서의 크래프트 리그닌의 저분자화

식물계 바이오매스는 석유로부터 얻어지는 화학물질들을 대체할 수 있는 물질로 제안되고 있다. 특히 식물계 바이오매스의 15-30%를 이루고 있는 리그닌은 복잡한 방향족 중합체로 이루어져 있어, 리그닌의 저분자화 공정에 의해 다양한 방향족 화합물을 얻을 수 있다. 본 연구에서는 국내에서 가장 많이 배출되는 크래프트 리그닌을 출발 물질로 선정하고, $^{13}C$-Muclear Magnetic Resonance($^{13}C$-NMR), Fourier Transform Infrared Spectroscopy (FT-IR), Elemental Analysis(EA)을 통해 원료물질의 화학적 구조를 분석하였다. 크래프트 리그닌의 저분자화 는 물-페놀 혼합 용매의 근임계 영역에서 수행되었으며, tube bomb reactor를 사용하였다. 최적의 반응조건을 찾기 위해 물-페놀의 비율, 반응온도($300-400^{\circ}C$)를 변화시키며 실험을 수행하였다. 또한 기체상 수소를 대신하여 수소발생 용매인 formic acid 사용에 따른 영향을 조사하였다. 액상 생성물의 화학 종류 및 양은 GC-MS를 통해 분석하였고, 고체 잔류물(char)은 FT-IR을 통해 분석하였다. GC-MS 분석 결과 페놀이 첨가된 경우 anisole, o-cresol(2-methylphenol), p-cresol(4-methylphenol), 2-ethylphenol, 4-ethylphenol, dibenzofuran, 3-methyl cabazole, xanthene이 생성되는 것을 확인하였다.