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Nugroho A.,Korea Institute of Science and Technology | Kim J.,Sungkyunkwan University | Kim J.,SKKU Advanced Institute of Nano Technology SAINT
Journal of Industrial and Engineering Chemistry

The effects of KOH on the supercritical hydrothermal synthesis of cobalt oxide and manganese oxide particles are investigated using a continuous-flow reactor. Significant changes in morphology, particle size, and oxidation state are observed by adding KOH. The spinel Co3O4 phase is transformed to a rocksalt CoO phase and the pyrolusite MnO2 phase is transformed to a hausmannite Mn3O4 phase in the presence of 0.5M KOH. The average particle size of the metal oxides decreased with an addition of KOH. The OH- ions of KOH may act as a reducing agent as well as a supersaturation enhancing agent under supercritical water conditions. © 2014 Published by Elsevier B.V. Source

Permana A.D.C.,Korea Institute of Science and Technology | Nugroho A.,Korea Institute of Science and Technology | Chung K.Y.,Korea Institute of Science and Technology | Chang W.,Korea Institute of Science and Technology | And 2 more authors.
Chemical Engineering Journal

Hierarchically porous anatase titanium oxide (TiO2) microspheres were synthesized using a green supercritical methanol route over a very short reaction time of 15min without using templates or surfactants. Primary nano-sized particles with diameters of 20-55nm with organic coverage on the surface were loosely aggregated and formed secondary micron-sized particles 1.0-2.5μm in diameter, creating a porous structure with average pores 9-15nm in diameter. When the as-synthesized microspheres were calcined under a Ar/5% H2 condition, carbonization of the organic groups formed an ultrathin and uniform carbon layer on the nano-sized primary particles with a thickness of 0.5-1nm and reduced some of the Ti4+ to Ti3+. Both the hierarchically porous structure and the conductive layer coating had positive effects by increasing Li ion storage capacity. The prepared TiO2 microspheres exhibited a high reversible discharge capacity of 212.3mAhg-1 at 0.1C, a high-rate performance of 77.9mAhg-1 at 8C, and an excellent capacity retention of >97% at the end of 100 cycles at 1.0C, whereas TiO2 nanoparticles without porous structure and surface modification exhibited lower discharge capacities of 161.8mAhg-1 at 0.1C and 5.2mAhg-1 at 8C, and poorer capacity retention of 26%. The considerable improvement in the electrochemical performance was attributed to the nano-sized TiO2 primary particles, porous structure, and carbon coating and Ti3+ incorporation. © 2013. Source

Susanti R.F.,Korea Institute of Science and Technology | Susanti R.F.,Parahyangan Catholic University | Han Y.S.,Korea Institute of Science and Technology | Kim J.,Sungkyunkwan University | And 3 more authors.
Journal of Membrane Science

Highly stable, uniform and ultrathin hydrophilic polymer coatings on the surface as well as in the pores of a PVDF microfiltration (MF) membrane are obtained by coating a hydrophilic monomer in liquid carbon dioxide (l-CO2) followed by subsequent crosslinking reaction. Polyethylene glycol diacrylate (PEGDA, Mn ~258g/mol) is used as the l-CO2 soluble hydrophilic monomer source and azobisisobutyronitrile (AIBN) was used as a radical initiator. The extremely low surface tension and the low viscosity of l-CO2 result in ultrathin and uniform PEG coatings on the hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane. The chemical composition, morphology, and the depth profiles of the PEG-coated membranes are characterized in detail using X-ray photoelectron spectroscopy, scanning electron microscopy, electron probe microanalysis and energy dispersive X-ray microanalysis. Long-term permeation flux test using a bovine serum albumin solution shows that the 1.0wt% PEGDA-coated membrane using l-CO2 exhibits 1.34 times larger BSA solution flux than that of the uncoated PVDF membrane, and 1.3 times larger flux than that of a commercial hydrophilic membrane. Fouling resistance estimation shows that the 1wt% PEGDA-coated membrane exhibits ~30% lower internal fouling resistance than the pristine membrane, and ~24% lower internal fouling resistance than the commercial hydrophilic membrane. © 2013. Source

Kim S.K.,Korea Institute of Science and Technology | Brand S.,Korea Institute of Science and Technology | Brand S.,Korean University of Science and Technology | Lee H.-S.,Korea Institute of Science and Technology | And 3 more authors.
Chemical Engineering Journal

The effects of varying reaction parameters on the hydrotreatment of soybean oil using Ni and CoMoS. x catalysts were investigated. The reactions were carried out in both batch and continuous reactors, at reaction temperatures of 300-440. °C, and hydrogen pressures of 2.5-15.0. MPa. The effects on hydrotreating conversion, gasoline/jet/diesel selectivity, and the degree of oxygen removal were investigated, to find optimum hydrotreatment conditions using both types of catalysts. Analyses of liquid composition, using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) and GC-flame ionization detection (FID), revealed that decarboxylation, decarbonylation, and hydrodeoxygenation reactions occurred competitively, and that each reaction pathway had different optimal conditions, as expected from the thermodynamic characteristics. The differences in the hydrotreatment reaction, liquid product compositions, and dominant reaction pathways between the batch and continuous reactions are also discussed. © 2013. Source

Kim S.K.,Korea Institute of Science and Technology | Han J.Y.,Korea Institute of Science and Technology | Hong S.-A.,Korea Institute of Science and Technology | Lee Y.-W.,Seoul National University | And 2 more authors.

Waste cooking oil (WCO) was purified by supercritical carbon dioxide (scCO2) extraction and catalytic hydrodeoxygenation of fresh soybean oil, WCO and scCO2-purified oil were studied for the synthesis of diesel-like hydrocarbons. The chemical compositions of the scCO 2-purified oils were very similar to those of fresh oil. Hydrotreating of WCO over the Pd and Ni catalysts showed lower conversions when compared to the NiMo and CoMo catalysts. The hydrotreating of scCO 2-purified oil using a Pd/Al2O3 catalyst resulted in 85.7% conversion, which is comparable to the 91.0% conversion from fresh oil whereas only 41.8% of WCO was converted under identical conditions. Hydrotreating of the scCO2-purified oil with other catalysts including Ni/SiO2-Al2O3, CoMo/Al 2O3 and NiMo/Al2O3 resulted in similar conversions in the range 84.4-92.9% compared to that from fresh oil. The scCO2-purification was effective for removing the various impurities in WCO, that were responsible for the detrimental effects on catalytic activity especially for the Pd and Ni catalysts. The origin of catalyst deactivation caused by the impurities in WCO is discussed. © 2013 Published by Elsevier Ltd. All rights reserved. Source

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