• Korean Chemical Engineering Research
• /
• v.60 no.3
• /
• pp.414-422
• /
• 2022

The objective of this work was to investigate the feasibility of acid-catalyzed hydrothermal fractionation for maximum solubilization of the hemicellulosic portion of two typical agricultural residues. The fractionation conditions converted into combined reaction severity (CS) in the range of 1.2-2.9 was used to establish a simple reaction criteria at glance. The hemicellulosic sugar yield of 56.6% was shown when rice straw was fractionated at the conditions at the conditions; 160 ℃ of temperature 0.75% (w/v) of H₂SO₄, 20 min of reaction time, 1:15 solid/liquid ratio. The hemicellulosic sugar yield of 83.0%, however, was achieved when barley straw was fractionated at the conditions at the conditions; 150 ℃ of temperature 0.75% (w/v) of H₂SO₄, and 15 min of reaction time, 1:10 solid/liquid ratio. For barley straw, acid-catalyzed hydrothermal fractionation could be effectively performed. After the fractionation process, the remaining fractionated solids were 48.5% and 57.5% from raw rice and barley straws, respectively. The XMG contents in the solid residues decreased from 17.3% and 17.6% to 6.0% and 2.6%, which corresponded to 16.7% and 8.5% on the basis of the raw straws, respectively. In another way, only 5.6% of cellulose and 8.5% of XMG were lost due to excessive decomposition during the acid-catalyzed hydrothermal fractionation of barley straw, compared to cellulose and XMG losses of 6.4% and 26.6% in rice straw. Hemicellulosic sugars from the rice straw were considered more over-decomposed due to the somewhat higher reaction severity at the acid-catalyzed hydrothermal fractionation.

• Korean Chemical Engineering Research
• /
• v.53 no.6
• /
• pp.802-807
• /
• 2015

In this study, we synthesized a new biocatalyst consisting of glucose oxidase (GOx), polyethyleneimine (PEI) and carbon nanotube (CNT) with addition of terephthalaldehyde (TPA) (TPA/GOx/PEI/CNT) for fabrication of glucose sensor that shows improved sensing ability and stability compared with that using other biocatalysts. Main bonding of the new TPA/GOx/PEI/CNT catalyst is formed by Aldol condensation reaction of functional end groups between GOx/PEI and TPA. Such formed bonding structure promotes oxidation reaction of glucose. Catalytic activity of TPA/GOx/PEI/CNT is evaluated quantitatively by electrochemical measurements. As a result of that, large sensitivity value of $41{\mu}Acm^{-2}mM^{-1}$ is gained. Regarding biosensor stability of TPA/GOx/PEI/CNT catalyst, covalent bonding formed between GOx/PEI and TPA prevents GOx molecules from becoming leaching-out and contributes improvement in biosensor stability. With estimation of the biosensor stability, it is found that the TPA/GOx/PEI/CNT catalyst keeps 94.6% of its initial activity even after three weeks.

• Journal of the Korean Applied Science and Technology
• /
• v.35 no.4
• /
• pp.1048-1056
• /
• 2018

Non-edible oil sources (i.e., Palm Acid Oil, waste animal fat) usually contain relatively high amount of free fatty acids (FFA) that make them inadequate for direct base catalyzed transesterification reaction. Enzymatic biodiesel synthesis can solve several problems posed by the alkaline-catalyzed transesterification, and has certain advantages over the chemical catalysis of transesterification, as it is less energy intensive, allows easy recovery of glycerol and the transesterification of glycerides with high free fatty acid contents. In this study, we synthesized biodiesel through enzymatic catalyzed process using high free fatty acid containing waste oil in biodiesel reactor (1 ton/day) and optimized the biodiesel production processes.

• Journal of Energy Engineering
• /
• v.4 no.3
• /
• pp.309-314
• /
• 1995

촉매의 담지순서 카본블랙의 종류 및 전처리 방법 등을 달리하여 연료전지 전극용 백금/카본 분말을 제조하고 이것의 백금 유실율, 백금 분산율 및 촉매 활성을 살표보았으며, 이를 사용하여 제조한 전극의 단위전지 성능을 상용전극과 비교하였다. 실험결과 카본블랙에 백금용액을 먼저 혼합한 후 환원시키는 전극제조 방법은 기존의 콜로이달법 보다 백금의 유실율이 적고 분산율이 높았다. 그리고 산/염기를 이용한 카본블랙의 전처리는 표면적은 줄어들지만 촉매활성을 증가시켰으며, 전극촉매의 최적 활성화 온도는 30$0^{\circ}C$이었다.

• Applied Chemistry for Engineering
• /
• v.2 no.4
• /
• pp.363-371
• /
• 1991

The catalytic performance and availability of heteropoly compounds for the conversion of methanol to hydrocarbons have been studied. The effects of reaction conditions such as reaction temperature, methanol partial pressure and residence time and the effects of ion-exchange of the catalysts were examined for enhancing the yield of hydrocarbons and the selectivity of low olefins. Their acid strength depended on the kind of countercation, and the yield of hydrocarbons and the selectivity for propylene to propane were closely related to the electronegativity of the corresponding countercations. In contrast to the other heteropoly compounds, the ammonium salt showed a considerably high catalytic activity and a high selectivity for paraffins to low olefins.

• Korean Chemical Engineering Research
• /
• v.56 no.1
• /
• pp.61-65
• /
• 2018

In this study, the conversion of glucosamine, which is a major monomer in chitin/chitosan of crustacean shell, using solid acid catalyst was performed to obtain chemical intermediates such as levulinic acid and 5-hydroxymethyl furfural (5-HMF). The conversion reaction was optimized with four reaction factors of selection of ionic resin catalyst, reaction temperature, catalyst amount, and reaction time. As an optimized result, the highest levulinic acid yield was achieved approximately 36.86% under the determined conditions (Amberlyst 15 as a solid-acid catalyst, $180^{\circ}C$, 5% catalyst amount and 60 min). On the other hand, 5-HMF yield was found to be 0.91% at the condition.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.387-390
• /
• 2008

Ni/MgAl 촉매상에서 LPG의 수증기 개질반응을 반응온도 $700{\sim}800^{\circ}C$, 공간속도 $20,000h^{-1}$, 수증기/탄소 비율 $1.0{\sim}3.0$인 조건으로 대기압하에서 수행하였다. 본 연구에서 사용된 촉매들은 공침법으로 제조하였으며, 하이드로탈사이트 구조에서 Ni-MgO 구조로 변환되는 과정에서 활성금속인 니켈이 고분산되는 장점을 지니고 있다. 제조된 촉매는 함침법으로 제조된 촉매보다 활성이 잘 유지되었으며 탄소침적에 대한 내구성 또한 향상되었으나 완벽하게 해결되지는 못하였다. 따라서 이와 같은 문제점을 해결하기 위해 귀금속이 modified된 Ni/MgAl 촉매를 제조하고 반응 특성을 비교하였다. Rh-Ni/MgAl 촉매는 LPG 수증기 개질 반응에서 1024시간동안 활성이 유지됨을 확인하였을 뿐만 아니라 탄소침적 또한 발생하지 않음을 확인하였다.

• Journal of Industrial Technology
• /
• v.29 no.A
• /
• pp.89-94
• /
• 2009

The efficiency of heterogeneous catalysts has been investigated in ozonation process for organic removal. Heterogeneous catalytic ozonation was conducted for the degradation of humic acid in the presence of Granular Activated Carbon or Zeolite as a solid catalyst. And the results were compared to those of ozonation alone and adsorption alone without ozonation. The degradation characteristics of humic acid in each process were examined with the values of pH, TOC, $UV_{254}$ and $COD_{Cr}$.

• Applied Chemistry for Engineering
• /
• v.5 no.1
• /
• pp.30-36
• /
• 1994

Reaction characteristics and correlations between the acidic property and catalytic activity of heteropoly acid catalyst on ETBE synthesis as a gasoline octane enhancer were investigated. The amount of pyridine adsorbed on heteropoly acid catalyst and catalytic activity in the synthesis of ETBE showed a good correlation. But ammonia failed to show such a correlation because of the complex formation of ammonia adsorbed and transition metal ions. In the case of supported catalyst catalytic activity and product distribution were mainly affected by the adsorption characteristics of TBA or iso-butene.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.1
• /
• pp.13-17
• /
• 2003

Cryogel and aerogel Pt-Ru/C were synthesized by the sol-gel process for the electrooxidation of methanol. From XRD analysis, it was found that the catalysts had highly dispersed Pt-Ru alloys on carbon support although high temperature treatments have been conducted. Electrocatalytic activities of 3 type aerogel catalysts were investigated in half cell experiments by cyclic voltammetry. Among them, Phloroglucinol-Formaldehyde(PF) type catalyst shows the highest activity. From the results of deactivation test for each catalysts, the aerogel catalysts are found to have excellent durability compared with those prepared by colloidal method.