• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.5
• /
• pp.419-426
• /
• 2018

$Ni-La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalysts with various $La_2O_3$ loading were investigated for hydrogen production from steam reforming of methane (SRM). The $La_2O_3$ loading influenced the physicochemical properties of $Ni-La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalysts such as BET surface area, Ni dispersion, Ni size and reducibility. Among the prepared catalysts, $Ni-70La_2O_3-Ce_{0.8}Zr_{0.2}O_2$ catalyst showed the highest activity and stability at a very high gas hourly space velocity (GHSV) of $932,556h^{-1}$. This is mainly due to high Ni dispersion, small Ni size and high reducibility.

• Economic and Environmental Geology
• /
• v.30 no.1
• /
• pp.1-14
• /
• 1997

The shales from the Euiseong area are interbedded along the bedding in Cretaceous Gyeongsang Supergroup, which are composed mainly of quartz, plagioclase, K-feldspar and associated with trace amount of biotite, muscovite, chlorite, pyrite, hematite, carbonate and clay minerals. The ratio of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shales from the Shindong Group are ranged from 9.16 to 24.32 and from 1.70 to 5.97, and the Hayang Group ranged from 2.76 to 8.89 and from 0.42 to 2.74, which are negative correlated between $K_2O/Na_2O$ and $Al_2O_3/Na_2O$ against $SiO_2/Al_2O_3$ respectively. Those are suggested that controlled of mineral compositions in shales due to substitution and migration of elements by sedimentation and diagenesis. These shale formation were deposited in basin of terrestrial environments originated from the igneous rocks, and the REE of these rocks are not influenced with diagenesis and hydrothermal alterations on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.43 to 0.62) and Th/U (1.11 to 10.71). The narrow range in trace and REE element characteristics as Co/Th (0.63 to 1.92), La/Sc (1.98 to 5.90), Sc/Th (0.58 to 1.30), V/Ni (0.90 to 3.25), Cr/V (0.45 to 1.78), Ni/Co (1.88 to 6.67) and Zr/Hf (30.04~60.87) of these shales argues for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (6.90 to 17.02), Th/Yb (4.17 to 13.68) and La/Th (1.98 to 5.90), and their origin is explained by derivation from a mixture of intermediate to acidic igneous rocks.

• Journal of the Korean Ceramic Society
• /
• v.45 no.12
• /
• pp.766-771
• /
• 2008

We fabricated single cells with a cathode consisting of a $LaNi_{0.6}Fe_{0.4}O_3-Ce_{0.8}Sm_{0.2}O_{1.9}$ composite (LNF-S20DC composite) active layer and an LNF current collecting layer on a ${0.89ZrO_2}-{0.10Sc_2}{O_3}-0.01{Al_2}{O_3}$ electrolyte sheet. The cathode layers were prepared by the screen-printing method. The cathode properties of these cells were measured by the AC impedance method at $800^{\circ}C$. The cathodes with the ceria-LNF composite active layer exhibited high power performance prior to current loading. We investigated the influence of the mixture ratio of LNF and S20DC on the cathodes properties. The Sm in the ceria particles of the composite cathode was substituted with other rare-earth elements. Cathodes with Pr and Gd co-doped ceria in the active layer provided the better performance than those with Sm- or Gd-doped ceria.

• Economic and Environmental Geology
• /
• v.30 no.5
• /
• pp.417-431
• /
• 1997

Characteristics of sedimentary rocks and enrichment of toxic elements in shale and coal from the Chungnam coal field were investigated based upon geochemistry of major, trace and rare earth elements. Shale and coal of the area are interbedded along the Traissic to the Jurassic Daedong Supergroup, which can be subdivided into grey shale, black shale and coal. The coal had been mined, however all the mines are abandonded due to the economic problems. The shale and coal are characterized by relatively low contents of $SiO_2$, and $Al_2O_3$ and high levels of loss-on-ignition (LOI), CaO and $Na_2O$ in comparison with the North American Shale Composite (NASC). Light rare earth elements (La, Ce, Yb and Lu) are highly enriched with the coal. Ratios of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shale and coal range from 30.0 to 351.8 and from 4.2 to 106.8, which have partly negative correlations against $SiO_2/Al_2O_3$ (1.24 to 6.06), respectively. Those are suggested that controls of mineral compositions in shale and coal can be due to substitution and migration of those elements by diagenesis and metamorphism. Shale and coal of the area may be deposited in terrestrial basin deduced from high C/S (39 to 895) and variable composition of organic carbon (0.39 to 18.40 wt.%) and low contents of reduced sulfur (0.01 to 0.05 wt.%). These shale and coal were originated from the high grade metamorphic and/or igneous rocks, and the rare earth elements of those rocks are slightly influenced with diagenesis and metamorphism on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.38 to 0.85) and Th/U (3.6 to 14.6). Characteristics of trace and rare earth elements as Co/Th (0.07 to 0.86), La/Sc (0.31 to 11.05), Se/Th (0.28 to 1.06), V/Ni (1.14 to 3.97), Cr/V (1.4 to 28.3), Ni/Co (2.12 to 8.00) and Zr/Hf (22.6~45.1) in the shale and coal argue for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (1.36 to 21.68), Th/Yb (3.5 to 20.0) and La/Th (0.31 to 7.89), and their origin is explained by derivation from a mixture of mainly acidic igneous and metamorphic rocks. Average concentrations in the shale and coal are As=7.2 and 7.5, Ba=913 and 974, Cr=500 and 145, Cu=20 and 26, Ni=38 and 35, Pb=30 and 36, and Zn=77 and 92 ppm, respectively, which are similar to those in the NASC. Average enrichment indices for major elements in the shale (0.79) and coal (0.77) are lower than those in the NASC. In addition, average enrichment index for rare earth elements in coal (2.39) is enriched rather than the shale (1.55). On the basis of the NASC, concentrations of minor and/or environmental toxic elements in the shale and coal were depleted of all the elements examined, excepting Cr, Pb, Rb and Th. Average enrichment indices of trace and/or potentially toxic elements (As, Cr, Cu, Ni, Pb, U and Zn) are 1.23 to 1.24 for shale and 1.06 to 1.22 for coal, respectively.

• Economic and Environmental Geology
• /
• v.31 no.4
• /
• pp.297-310
• /
• 1998

Geochemical characteristics of environmental toxic elements at the Narim mine area were investigated on the basis of major, minor, rare earth element geochemistry and mineralogy. Ratios of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in soils and sediments range from 11.57 to 22.21 and from 1.86 to 3.93, and are partly negative and positive correlation against $SiO_2/Al_2O_3$ (3.41 to 4.78), respectively. These suggested that sediment source of host granitic gneiss could be due to rocks of high grade metamorphism originated by sedimentary rocks. Characteristics of some trace and rare earth elements of V/Ni (0.33 to 1.95), Ni/Co (2.00 to 6.50), Zr/Hf (11.27 to 53.10), La/Ce (0.44 to 0.55), Th/Yb (4.07 to 7.14), La/Th (2.35 to 3.93), $La_N/Yb_N$ (6.58 to 13.67), Co/Th (0.63 to 2.68), La/Sc (3.29 to 5.94) and Sc/Th (0.49 to 1.00) are revealed a narrow range and homogeneous compositions may be explained by simple source lithology. Major elements in all samples are enriched $Al_2O_3$, MgO, $TiO_2$ and LOI, especially $Fe_2O_3$ (mean=7.36 wt.%) in sediments than the composition of host granitic gneiss. The average enrichment indices of major and rare earth elements from the mining drainage are 2.05 and 2.91 of the sediments and are 2.02 and 2.60 of the soils, normalizing by composition of host granitic gneiss, respectively. Average composition (ppm) of minor and/or environmental toxic elements in sediments and soils are Ag=14 and 1, As=199 and 14, Cd=22 and 1, Cu=215 and 42, Pb=1770 and 65, Sb=18 and 3, Zn=3333 and 170, respectively, and extremely high concentrations are found in the subsurface sediments near the ore dump. Environmental toxic elements were strongly enriched in all samples, especially As, Cd, Cu, Pb, Sb and Zn. The level of enrichment was very severe in mining drainage sediments, while it was not so great in the soils. Based on the EPA value, enrichment index of toxic elements is 8.63 of mining drainage sediments and 0.54 of soils on the mining drainage. Mineral composition of soils and sediments near the mining area were partly variable being composed of quartz, mica, feldspar, amphibole, chlorite and clay minerals. From the gravity separated mineralogy, soils and sediments are composed of some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, goethite and various hydroxide minerals.