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Activated Carbon Fibers from Chemically Modified Coal Tar Pitches
S.K. Ryu,J.W. Shim,K.S. Yang,I. Mochida 한국탄소학회 2000 Carbon Letters Vol.1 No.1
Coal tar pitch was chemically modified with 10 wt% benzoquinone (BQ) to raise the softening point of isotropic pitch precursor and the precursor was melt-spun into pitch fibers, stabilized, carbonized and activated with steam at 900℃. The weight loss of carbon fiber-benzoquinone (CF-BQ) increased with the increase of activation time like other fibers, but was lower than those of Kureha fiber at the same activation time in spite of larger geometric surface area. Those adsorption isotherms fitted into 'Type I' according to Brunauer, Deming, Deming and Teller classification. However, there was very thin low-pressure hysteresis that lower closure points of the hysteresis are about 0.42-0.45. From the pore size distribution curves, there might be some micropores having narrow-necked bottle; a series of interconnected pore is more likely than discrete bottles. FT-IR studies showed that the functional groups such as carboxyl, quinone, and phenol were introduced to ACFs-BQ surface after steam activation. Methylene blue decolorization and iodine adsorption capacity of ACF-BQ increased linearly with the increase of specific surface area and was larger than that of ACF-Kureha at the same specific surface area.
Activated Carbon Fibers from Chemically Modified Coal Tar Pitches
Ryu, S.K.,Shim, J.W.,Yang, K.S.,Mochida, I. Korean Carbon Society 2000 Carbon Letters Vol.1 No.1
Coal tar pitch was chemically modified with 10 wt% benzoquinone (BQ) to raise the softening point of isotropic pitch precursor and the precursor was melt-spun into pitch fibers, stabilized, carbonized and activated with steam at $900^{\circ}C$. The weight loss of carbon fiber-benzoquinone (CF-BQ) increased with the increase of activation time like other fibers, but was lower than those of Kureha fiber at the same activation time in spite of larger geometric surface area. Those adsorption isotherms fitted into 'Type I' according to Brunauer, Deming, Deming and Teller classification. However, there was very thin low-pressure hysteresis that lower closure points of the hysteresis are about 0.42-0.45. From the pore size distribution curves, there might be some micropores having narrow-necked bottle; a series of interconnected pore is more likely than discrete bottles. FT-IR studies showed that the functional groups such as carboxyl, quinone, and phenol were introduced to ACFs-BQ surface after steam activation. Methylene blue decolorization and iodine adsorption capacity of ACF-BQ increased linearly with the increase of specific surface area and was larger than that of ACF-Kureha at the same specific surface area.
Kim, T.,Ham, C.,Rhee, C.K.,Yoon, S.H.,Tsuji, M.,Mochida, I. Pergamon Press ; Elsevier Science Ltd 2009 Carbon Vol.47 No.1
Correlations between the electrochemical double layer capacitances of various acetylene blacks modified by surface oxidation and heat treatment, and their morphologies are presented. The acetylene blacks were different from each other in primary structural unit size (equivalent to mean particle diameter). They were oxidized in air at 300<SUP>o</SUP>C for 1h to produce graphene sheets protruding from the surfaces of the spherical particles. In addition, the surfaces of the acetylene blacks were modified by heat treatments from 1000<SUP>o</SUP>C to 2800<SUP>o</SUP>C, which resulted in a morphological change from surfaces covered with protruding graphene sheets to ones wrapped with basal planes of graphite. Correlations between the capacitances of the acetylene blacks and the observed morphologies showed that the surface covered with protruding graphene sheets was roughly 10 times more effective in capacitive charging than the surface of graphite basal planes. Specifically, the surface specific capacitance of the edged-graphene-sheet-covering surface was 146mF/m<SUP>2</SUP>, while that of the basal-planes-wrapping surface was 16mF/m<SUP>2</SUP>. It was concluded that the capacitances of the acetylene blacks were mainly defined by surface morphology, which were in turn influenced by structural unit size and degree of oxidation.
Lee, K.J.,Shiratori, N.,Lee, G.H.,Miyawaki, J.,Mochida, I.,Yoon, S.H.,Jang, J. Pergamon Press ; Elsevier Science Ltd 2010 Carbon Vol.48 No.15
Electrospun polyacrylonitrile (PAN)-based nanofiber with a uniform diameter of ca. 800nm was carbonized and steam-activated to produce activated carbon nanofiber with tailored microporosity and abundant nitrogen-containing functional groups as highly efficient adsorption sites. A remarkable amount of formaldehyde, a typical indoor pollutant, was adsorbed onto the pore surface of the PAN-based activated carbon nanofibers even at a low concentration (ca. 11ppm), demonstrating more than twice as long as breakthrough time of formaldehyde adsorption as compared to conventional activated carbon fibers of larger fiber diameter. The tailored shallow microporosity was considered to afford the preferential adsorption of formaldehyde also in a humid environment.
Deep desulfurization of gas oil over NiMoS catalysts supported on alumina coated USY-zeolite
Nakano, K.,Ali, S.A.,Kim, H.J.,Kim, T.,Alhooshani, K.,Park, J.I.,Mochida, I. Elsevier Scientific Pub. Co 2013 Fuel processing technology Vol.116 No.-
A series of NiMoS catalysts supported on USY-zeolite coated with different amounts of alumina were prepared and evaluated for deep hydrodesulfurization (HDS) of gas oil using a flow reactor system in single- and dual-bed configurations. The performance of these catalysts was compared to the conventional HDS catalyst as well as to NiMoS catalyst supported on physical mixture of alumina and USY-zeolite. Physically mixed alumina and USY zeolite showed high HDS activity, but it was accompanied with significant cracking of hydrocarbons. Activity and kinetic analysis showed that heavy coating of alumina on the zeolite resulted in much lower HDS and cracking activity. On the other hand, very light coating of alumina on the zeolite resulted in catalytic behavior similar to that of physical mixture of USY-zeolite and alumina. The general trend was an increase in HDS as well as hydrocracking activity with the decrease in amount of alumina coating over zeolite. Changes in product density, aromatic content, mid-boiling point, cetane index, and molecular weight also reflected this trend. The results of this study indicate that catalysts with neither too low nor too high amount of alumina coating on the USY zeolite are suitable to achieve the balance between high HDS and low cracking activities. The highlight of the present study is that it confirmed the deep HDS activity of USY containing alumina supports in the flow reactor system which is industrially applied. In addition, the stability test confirmed the long-term performance of alumina-coated zeolite catalyst.