• 한국재료학회지
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• 제34권7호
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• pp.341-354
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• 2024

Today, the principles of green chemistry are being fundamentally applied in the chemical industry, such as the nitrobenzene industry, which is an essential intermediate for various commercial products. Research on the application of response surface methodology (RSM) to optimize nitrobenzene synthesis was conducted using a sulfated silica (SO₄/SiO₂) catalyst and batch microwave reactor. The nitrobenzene synthesis process was carried out according to RSM using a central composite design (CCD) design for three independent variables, consisting of sulfuric acid concentration on the silica (%), stirring time (min), and reaction temperature (℃), and the response variable of nitrobenzene yield (%). The results showed that a three-factorial design using the response surface method could determine the optimum conditions for obtaining nitrobenzene products in a batch microwave reactor. The optimum condition for a nitrobenzene yield of 63.38 % can be obtained at a sulfuric acid concentration on the silica of 91.20 %, stirring time of 140.45 min, and reaction temperature of 58.14 ℃. From the 20 experiments conducted, the SO₄/SiO₂ catalyst showed a selectivity of 100 %, which means that this solid acid catalyst can potentially work well in converting benzene to nitrobenzene.

• 한국분말재료학회지
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• 제9권5호
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• pp.365-369
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• 2002

Silica hydrogel was synthesized by the reaction of liquid sodium silicate with sulfuric acid. The condensation polymerization of the synthesized hydrogel was carried out via an aging process under the acidic or alkaline conditions. Nano porous silica with the pore size below 3 nm and surface area of $715m^2/g$, was obtained by the above processes in acidic ranges(pH : 3~5). The pore size and surface area of the silica varied with pH, and in alkaline ranges(pH : 8~10), those were 21 nm and $300m^2/g$ respectively. The characteristics of the silica varied with the thermal treatment which caused the change of surface area, pore volume and pore diameter.

• 펄프종이기술
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• 제32권1호
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• pp.33-40
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• 2000

The effectiveness of silica-based microgels prepared through the reaction of sulfuric acid and sodium silicate as a component of Compozil system has been evaluated . Silica based microgels with better performance in retention and drainage than a commercial colloidal silica sol have been successfully prepared. Silica gels with the highest charge density were obtained when product pH was controlled to 9. And highly charged silica-based microgels showed greater retention and freeness performance than a commerical product. In particular the difference in retention, turbidity , and freeness between these microgels and a commercial product was eminent at low addition rate. The effects of reaction conditions including reaction temperature, process water quality and feeing rate on product efficiency in improving retention and drainage were also investigated and discussed.

• 콘크리트학회지
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• 제9권5호
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• pp.127-135
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• 1997

본 연구는 규사분말을 치환한 콘크리트의 내산성에 관한 실험적 연구로서 내산성능 개선을 위한 혼화재로서 규사 분말의 치환시 콘크리트의 시공성 및 내산성 실험결과 다음과 같은 결론을 얻었다. 황산에 침지된 콘크리트의 내산성 실험결과 혼화재의 종류 및 치환량에 따른 내산성은 규사분말을 10~15% 치환한 SS시험체가 GS 및 SF시험체와 비교하여 강도 저하, 중량 감소, 외관 변화, 중성화 깊이 증가, 시험체 내부의 pH저하 등에서 우수하게 나타났다. 물결합재비의 변화에 따른 내산성은 물결합재비 60%의 경우보다 40% 높게 나타나 물결합재비가 낮을수록 내산 성능이 향상됨을 알 수 있었다. 이는 규사 분말의 공극충전효과 및 산에 침해되지 않는 결정성 SiO2로서의 특성 때문으로 사료된다. 규사 분말을 적적량 치환한 콘크리트는 시공성 및 강도 발현 측면에서 보통 포틀랜트시멘트를 사용한 PL시험체와 비교하여 동등 이상이며, 내산성은 슬래그시멘트를 사용한 GS 및 실리카흄을 혼화재로 치환한 SF시험체보다 우수함을 알 수 있었다. 그러므로 규사 분말을 적정량 치환한 콘크리트를 산류의 침해가 예상되는 부위에 시공하였을 때 콘크리트의 내산성 증진 효과를 얻을 수 있을 것으로 사료된다.

• 한국미생물·생명공학회지
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• 제18권1호
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• pp.35-38
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• 1990

정제된 저해물질의 Rf치는 0.12-0.71 사이였으며 melting point는 154.3-155.3$^{\circ}C$로 나타났다. 물, formic acid, ethylene glycol monomethyl ether에는 용해되지만 그외 대부분의 용매에서는 불용성이었고 흡습성이 매우 큰 물질이었다. Phenol-sulfuric acid, ninhydrin, silvernitrate-sodium hydroxide 반응은 양성이었으나, DNS 반응에서는 음성이며 자외선 조사하에서 형광을 나타내었다. 저해물질의 구성성분은 fructose와 aspartic acid로 확인되었으며 분자량이 약 1,050 정도였다.

• Elastomers and Composites
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• 제52권4호
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• pp.242-248
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• 2017

Wet masterbatch (WMB) technology is studied to develop high-content and highly disperse silica-filled compounds. This technology refers to the solidification of surface-modified silica with a rubber solution or latex. Until now, researchs based on styrene butadiene rubber (SBR)/silica WMB has been mainly performed. However, the blending of SBR/silica WMB and BR is not known and is currently under research and development. Therefore, in this study, the BR blending method suitable for emulsion (ESBR)/silica WMB is investigated by measuring their cure characteristics and the mechanical and dynamic viscoelastic properties. As a result, it was confirmed that the blending of ESBR/silica WMB and BR/silica dry masterbatch is most appropriate. However, it showed a disadvantage compared with the conventional mixing method, which was due to the surfactant remained and the sulfuric acid used as the coagulant.

• 펄프종이기술
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• 제35권5호
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• pp.1-9
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• 2003

Effectiveness of the microparticle retention systems in improving drainage, retention, formation has been recognized for many years. In this study the effectiveness of crosslinked cationic corn starches and silica-based microgels as components of Compozil system has been evaluated. It was shown that improvements in retention and strength could be achieved by employing crosslinked cationic corn starches especially at high conductivity. Silica-based microgels with better performance in retention and drainage than a commercial colloidal silica sol have been made through a reaction of sulfuric acid and sodium silicate solutions.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Proceedings of Pre-symposium of the 10th ISWPC
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• pp.43-49
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• 1999

Effectiveness of the microparticle retention systems in improving dramage, retention, formation has been recognized for many years (1, 2, 3, 4, 5). In this study the effectiveness of crosslinked cationic corn starches and silica-based microgels as components of Compozil system has been evaluated. It was shown that improvements in retention and strength could be achieved by employing crosslinked cationic corn starches especially at high conductivity. Silica-based microgels with better performance in retention and dramage than a commercial colloidal silica sol have been made through a reaction of sulfuric acid and sodium silicate solutions.

• Korean Membrane Journal
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• 제6권1호
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• pp.44-54
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• 2004

Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

• 공업화학
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• 제28권3호
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• pp.360-368
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• 2017

고기능성 폴리머 콘크리트 복합재료의 내구성을 조사하기 위하여 올소타입 불포화폴리에스테르 수지와 이소타입 불포화폴리에스테르 수지를 폴리머 결합재로 사용하였고, 탄산칼슘과 실리카 미분말을 충전재로 사용하여 공시체를 제작하고 내열수성, 내약품성, 세공분석 및 SEM 조사를 실시하였다. 이소타입 불포화폴리에스테르 수지를 사용한 공시체의 압축강도가 올소타입 불포화폴리에스테스 수지를 사용한 공시체의 압축강도보다 높은 것으로 나타났고, 탄산칼슘 충전재에 비하여 실리카 미분말을 사용한 공시체의 압축강도가 높게 나타났다. 내열수성 시험에서 이소타입 불포화폴리에스테르 수지를 사용한 공시체가 올소타입 불포화폴리에스테르 수지를 사용한 공시체보다 내열수성이 우수한 것으로 나타났고, 탄산칼슘 충전재를 사용한 공시체가 실리카 미분말을 사용한 공시체보다 내열수성이 우수한 것으로 나타났다. 내약품성 시험 후에 측정한 압축강도 감소율은 수산화나트륨 수용액에 의한 압축강도 감소율이 가장 크게 나타났고 다음으로 황산, 염산 및 염화칼슘 순으로 나타났다. 알칼리성인 수산화나트륨 수용액에서는 탄산칼슘을 충전재로 사용한 공시체가 실리카 미분말을 사용한 공시체보다 중량 감소율이 적게 나타났으나 황산과 염산의 산성시약에서는 실리카 미분말을 사용한 공시체가 탄산칼슘을 사용한 공시체보다 중량 감소율이 적게 나타났다.