• 청정기술
• /
• 제16권1호
• /
• pp.19-25
• /
• 2010

결정성의 셀룰로우스를 수소분위기하에서 다양한 귀금속 촉매를 이용하여 폴리올로 전환시키는 연구를 수행하였다. 촉매는 단일 귀금속(Pt, Ru, Ir, Rh, Pd)을 활성탄에 습식함침법으로 담지시켜서 제조하였으며, Pt/$\gamma-Al_2O_3$와 Pt/H-mordenite를 비교촉매로 사용하였다. 생성물은 고압액체크로마토그래피로 분석하였다. 촉매는 질소흡착, X-선 회절법, 유도결합플라즈마분광법(ICP-AES), 수소-승원환원분석($H_2$-TPR), 그리고 일산화탄소 화학흡착을 통하여 분석하였다. 셀룰로우스의 전환율은 사용한 촉매와 연관관계가 낮은 것으로 나타났으며 활성탄에 담지된 귀금속 촉매중에서 Pt/AC가 높은 폴리올의 수득률에 바람직한 것으로 조사되었다.

• 펄프종이기술
• /
• 제45권2호
• /
• pp.56-65
• /
• 2013

Electron beam treatment was applied for improving dissolution of cellulose with ionic liquids. Two ionic liquids, 1-allyl-3-methylimidazolium chloride ([Amim]Cl]: AC) and 1,3-dimethylimidazolium methylphosphite ([Dmim][$(MeO)(H)PO_2$]: Me) were used for this experiment. Treatment with electron beams up to dose of 400 kGy resulted in the increase of hot water extract and alkali extract of cotton pulp and the great reduction in the molecular weight of cellulose. For the dissolution of cotton pulp with two ionic liquids, the electron beam treated samples showed faster dissolution. The dissolved cellulose with Me ionic liquid were regenerated with acetonitrile and the structure of regenerated cellulose showed distinct difference depending on the electron beam treatment. Those results provide the electron beam pre-treatment could be applied as an energy efficient and environmentally benign method to increase the dissolution of cellulose with ionic liquids.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제10권4호
• /
• pp.346-352
• /
• 2005

The chemical characteristics, enzymatic saccharification, and ethanol fermentation of autohydrolyzed lignocellulosic material that was exposed to steam explosion were investigated using bagasse as the sample. The effects of the steam explosion on the change in pH, organic acids production, degrees of polymerization and crystallinity of the cellulose component, and the amount of extractive components in the autohydrolyzated bagasse were examined. The steam explosion decreased the degree of polymerzation up to about 700 but increased the degree of crystallinity and the micelle width of the cellulose component in the bagasse. The steam explosion, at a pressure of 2.55 MPa for 3 mins, was the most effective for the delignification of bagasse. 40 g/L of glucose and 20 g/L of xylose were produced from 100 g/L of the autohydrolyzed bagasse by the enzymatic saccharification using mixed cellulases, acucelase and meicelase. The maximum ethanol concentration, 20 g/L, was obtained from the enzymatic hydrolyzate of 100 g/L of the autohydrolyzed bagasse by the ethanol fermentation using Pichia stipitis CBS 5773; the ethanol yield from sugars was 0.33 g/g sugars.

• Journal of Biosystems Engineering
• /
• 제43권1호
• /
• pp.59-71
• /
• 2018

Purpose: Cellulose nanocrystals (CNCs) are natural polymers that have been promoted as a next generation of new, sustainable materials. CNCs are invaluable as reinforcing materials for composites because they can impart improved mechanical, chemical, and thermal properties and they are biodegradable. The purpose of this review is to provide researchers with information that can assist in the application of CNCs extracted from waste agricultural byproducts (e.g. rice husks, corncobs, pineapple leaves). Methods & Results: This paper presents the unique characteristics of CNCs based on agricultural byproducts, and lists processing methods for manufacturing CNCs from agricultural byproducts. Various mechanical treatments (microfluidization and homogenization) and chemical treatments (alkali treatment, bleaching and hydrolysis) can be performed in order to generate nanocellulose. CNC-based composite properties and various applications are also discussed. Conclusions: CNC-based composites from agricultural byproducts can be combined to meet end-use applications such as sensors, batteries, films, food packaging, and 3D printing by utilizing their properties. The review discusses applications in food engineering, biological engineering, and cellulose-based hydrogels.

• 대한화학회지
• /
• 제4권1호
• /
• pp.44-50
• /
• 1957

Fibrous cellulose triacetate prepared from purified cotton under various temperatures was dissolved in the solution of 70%, monochloroacetic acid and it was fractionated using water as a precipitant. Eight fractions were obtained through the stepwise precipitation. Degree of polymerization and molecular weight of each fraction were measured viscometrically. Integral and differential molecular weight distribution curve were drawn for each sample prepared under various temperatures and were carefully observed. On this experimental study, following conclusions were obtained: Fractional precipitation can be carried out for fibrous cellulose triacetate in the solution of 70% monochloroacetic acid using water as a precipitant. The differences on the shapes of molecular weight distribution curve were occured on account of the various acetylation temperatures. At the relatively higher acetylation temperatures, the cellulose was randomly degraded and the portion of low degree of polymerization was increased. Commercial acetate, therefore, may not be prepared at above 40$^{\circ}C$ according to the molecular weight distribution curve regardless of higher viscosity and average degree of polymerization. It was concluded that the optimum acetylation temperature for commercial acetate was approximately 30$^{\circ}C$.

• Elastomers and Composites
• /
• 제53권1호
• /
• pp.6-12
• /
• 2018

Styrene-butadiene Rubber (SBR) Latex composites, incorporated with cellulose/starch-silica hybrids synthesized by gel-adsorption method, were filled into rubber by the latex compounding method. The structure morphology, mechanical properties, and thermodynamic properties of gel-silica hybrids were characterized. The states of hybrids which used as fillers were also characterized by SEM. As the fillers ratio increased, the difference for storage modulus of samples had been morphology by rubber process analyzer (RPA). Then, as more fillers ratio was filled into the matrix, the best tensile strength result, and the largest modulus value were also proved by UTM and RPA. As for thermal stability, increase in the ratio of fillers led to higher initial decomposition temperature, which was also proved by TGA. The swelling ratio of samples has also been characterized. From the results of all the tests, cellulose-silica hybrid showed the best results as a filler, and the best filling ratio of this hybrid is about 10 phr, which has the best storage modulus and great tensile strength.

• Bulletin of the Korean Chemical Society
• /
• 제33권12호
• /
• pp.4122-4126
• /
• 2012

Cellulose-graft-poly (L-lactide) (cellulose-g-PLLA) was successfully prepared via ring-opening polymerization (ROP) by using 4-dimethylaminopyridine (DMAP) as an organic catalyst in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The structure and morphology of the polymer was characterized by nuclear magnetic resonance (NMR) and transmission electron microscope (TEM). From wide-angle X-ray powder diffraction (WAXD) and degradation test (by acid, alkaline, PBS and enzyme solution), changes in the crystalline structure as a result of degradation was also investigated. The results indicated that materials which have low degree of crystallinity showing higher degradability, however, in acid liquor, enzyme solution, alkaline liquor and PBS system, the degradation rate of the polymer decreased by the above sequence. Moreover, with the further increase of graft degree of this material, its degradation degree decreased.

• 한국군사과학기술학회지
• /
• 제27권4호
• /
• pp.528-534
• /
• 2024

In continuous research of detecting highly toxic chemical warfare agents to ensure preparedness for the future battlefield, flexible and wearable sensor platforms with high sensitivity are still demanding. Herein we demonstrate a facile fabrication of polypyrrole-based chemiresistors on cellulose paper for the detection of nerve gas simulants. In order to optimize electrical properties of sensor platform, conducting polymer made of polypyrrole were first synthesized on flexible cellulose paper and interdigitated electrodes were formed thereon. Following confirmation of polypyrrole and/or oxime moiety through FT-IR analyses, electrical characteristics were measured in the various ratio of monomers between simple pyrrole and oxime-modified one. Typically for the optimized chemiresistor(2:8 molar ratio of simple pyrrole and oxime-modified one), eleven species of chemical warfare agents were examined and enhanced conductivity(10⁴~10⁵ order) was observed for three simulants(diethyl cyanophosphonate, diisopropyl fluorophosphonate and diethyl chlorophosphonate), which was mainly attributed to intermolecular hydrogen bonding, while no significant responses was recorded against sixteen common volatile organic chemicals.

• KSBB Journal
• /
• 제13권6호
• /
• pp.687-692
• /
• 1998

본 연구는 초임계 이산화탄소를 이용한 섬유소의 효소 가수분해에서 효소의 안정성 및 반응조건에 관한 연구를 수행하였다. 초임계 이산화탄소에서 cellulase의 안정성에 대한 실헝결과 압력에 대한 영향에서는 80 atm에서 160 atm까지 효소의 안정성이 유지되었으며 200 atm 에서는 약간 감소하였다. 반응시간의 경우에는 150분까지 효소의 활성이 그대로 유지되었으며, 온도는 상압에서의 최적온도인 $50^{\circ}C$ 까지는 효소의 활성이 유지되었으나 그 이상의 온도에서는 효소의 변성에 의하여 활성이 감소하였다, 초임계 이산화탄소에서 cellulose를 120 atm과 $50^{\circ}C$ 애서 90분간 cellulase로 가수분해 반응을 수행한 결과 20 g/L 의 Avicel이 완전히 가수분해되어 100% 수율의 glucose블 얻을 수 있었으며, 이는 상압에서 보다 glucose 수율이 1.5배 증가한 결과이다. 반면에 cellulose fiber인 경우는 상압에서 보마 1.9배 증가하였다. 통일 조건에서 Avicel의 농드를 60 g/L로 한 경우에는 glucose 수율이 상압에서 보다 1.2배 증가하였다.

• 펄프종이기술
• /
• 제45권3호
• /
• pp.59-68
• /
• 2013

The cotton contains various impurities such as protein, wax, pectins, coloring matter, even though cotton has been a major source of pure cellulose. The purification processes have been commonly applied to obtain the pure cellulose. However the excessive purification treatments could lead to the damage in the cellulose structure which could result in the degradation of cellulose and the limited application of cotton cellulose. In this study, the changes in cellulose structural properties such as crystallinity and DP(degree of polymerization) by the various conditions of the purification processes were investigated. The less toxic agents such as hydrogen peroxide and sodium silicate were applied for the purification treatment in this study. The increase in the process times, the temperature and the applied amount of chemical agents resulted in the more purified cellulose. The DP of cotton cellulose was increased at the first weak conditions by the reduction of small molecules such as pectin, wax, and so on. Especially the 2 % addition amount of $H_2O_2$ with $Na_2SiO_3$ resulted in the higher value in the DP and the brightness compared to the 1.5 % addition amount of $H_2O_2$. However, the 4 % addition amount of $H_2O_2$ with $Na_2SiO_3$ showed the decreased value because of excessive treatment. In case of the changes in the crystallinity (Gjk), the highest value of the crystallinity was obtained by the 2% addition amount of $H_2O_2$ on the cotton cellulose, which showed similar with the change in the DP.