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RISS 인기검색어
- 검색키워드
- 저자 : Takuya Kitaoka (검색결과 5 건)
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Takuya Kitaoka,Hiroo Tanaka 한국펄프·종이공학회 1999 한국펄프종이학회 기타 간행물 Vol.- No.-
Aluminum sulfate (alum) as a representative retention aid in papermaking processes was added to pulp suspensions, and the aluminum components adsorbed on the pulp were investigated quantitatively by two types of X-ray elementary analyses with regard to simultaneous changes of their surface charges. Xray photoelectron spectroscopy (XPS) and X-ray fluorescence analysis (XFA) were applied to determine the aluminum components retained in pulp pads up to ca. 10 nm and 100 11m depth, respectively. In other words, XPS was utilized to analyze the outermost surface layers of the samples, and XFA was available for measurement of their extensive regions. A particle charge detector (PCD) was used to monitor streaming potentials at various pHs of the pulp mixtures under moderate sharing conditions. At pH 4.5 of pulp suspensions containing alum, surface charges of pulp fibers varied from negative to slight negative (approximately neutral) according to adsorption of aluminum components onto the pulp fibers. Subsequently, when a dilute NaOH solution in limited amounts was added to pulp mixtures. both streaming potentials and surface aluminum content of the pulp fibers increased distinctly although little total aluminum retention increased. Further addition of alkali solutions brought drastic decreases of the surface charges and surface aluminum content, while total aluminum content, on the contrary. increased gradually under neutral conditions.<br/> These results indicate that residual aluminum ions remained in pulp suspensions are predominantly adsorbed on surfaces of pulp fibers by adequate alkali additions, and they must sufficiently cationize the fiber surfaces with increases of somewhat cationic aluminum complexes formed on the surfaces. On the other hand, aluminum components formed in higher pH ranges have nearly no contribution to improvement of charge properties of the pulp fiber surfaces, even though aluminum retention in pulp pads increases. XPS and XFA analyses combined with streaming potential measurement using a PCD suggest close relationships between aluminum content on the pulp fiber surfaces and their charge properties.
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Paper-structured Catalysts with Porous Fiber Networks for Fischer-Tropsch Synthesis
Ayami Saimura,Takuya Kitaoka 한국펄프·종이공학회 2016 펄프.종이기술 Vol.48 No.6
The Fischer-Tropsch synthesis (FTS) is a promising catalytic process for converting syngas (hydrogen and carbon monoxide (CO)) into valuable hydrocarbons for use as fuels and fine chemicals. However, the FTS reaction is highly exothermic; hence careful process control is required to promote smooth gas flow and avoid the formation of local hot spots inside the catalyst layer. In this work, cobalt (Co)-based paper-structured catalysts with micrometer-size pores were prepared via a papermaking technique and an impregnation method. The FTS reaction was carried out using Co-containing paper composites having different Co loadings, residence times and stacking patterns to investigate the effects of the catalyst layer design on the FTS catalytic efficiency. Catalytically-active metallic Co nanoparticles were successfully synthesized inside the porous fiber networks of the flexible and easy-to-handle paper composites. An alternate stacking arrangement of five Co papers and a designated number of catalyst-free ceramic papers demonstrated higher CO conversion than stacks of the Co papers alone without ceramic spacing layers, despite the same total Co loading and gas residence time inside the catalyst layers. It was assumed that the catalyst-free ceramic papers with porous fiber networks effectively promoted the diffusion of both gas and heat during the exothermic FTS processes. Our paper-structured catalysts with a unique porous architecture allowed fine-tuning of the catalyst layers by stacking the various paper composites. These results are expected to advance catalytic FTS process engineering.
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Hiroo Tanaka,Hideaki Ichiura,Takuya Kitaoka 한국펄프·종이공학회 1999 한국펄프종이학회 기타 간행물 Vol.- No.-
A cationic demand (CD) is a very useful indication for determining the optimum dosage rate of retention aids to the papermaking stock at the wet end. Polyelectrolyte titration has been most often used to determine a CD. Highly accurate results can be obtained by this method when the ionic strength of sample is low. But this is accompanied by the serious errors when the ionic strength is higher than that corresponding to 20 milli molar (mM) monovalent, 2 mM divalent or 0.2 mM trivalent ions because of no occurrence of the end point of titration. Therefore. it is very difficult or almost impossible for the conventional method to be applied to the industrial suspensions such as papermaking stock and industrial waste water. Then a novel method using chromophoric labeled cationic polymer which can be applicable to the sample with high ionic strength has been developed.
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