Energy Efficient and Intermittently Variable Ammonia Synthesis over Mesoporous Carbon-Supported Cs-Ru Nanocatalysts

The Cs-promoted Ru nanocatalysts supported on mesoporous carbon materials (denoted as Cs-Ru/MPC) and microporous activated carbon materials (denoted as Cs-Ru/AC) were prepared for the sustainable synthesis of ammonia under mild reaction conditions (<500 °C, 1 MPa). Both Ru and Cs species were homogeneously impregnated into the mesostructures of three commercial available mesoporous carbon materials annealed at 1500, 1800 and 2100 °C (termed MPC-15, MPC-18 and MPC-21, respectively), resulting in a series of Cs-Ru/MPC catalysts with Ru loadings of 2.5–10 wt % and a fixed Cs loading of 33 wt %, corresponding to Cs/Ru molar ratios of 2.5–10. However, the Ru and Cs species are larger than the pore mouths of microporous activated carbon (shortly termed AC) and, as a consequence, were mostly aggregated on the outer surface of the Cs-Ru/AC catalysts. The Cs-Ru/MPC catalysts are superior to the Cs-Ru/AC catalyst in catalysing mild ammonia synthesis, especially for the 2.5Cs-10Ru/MPC-18 catalyst with a Ru loading of 10 wt % and a Cs/Ru ratio of 2.5, which exhibited the highest activity across a wide SV range. It also showed an excellent response and stability during cycling tests over a severe temperature jump in a short time, presumably due to the open mesoporous carbon framework and suitable surface concentrations of CsOH and metallic Ru species at the catalytically active sites. This 2.5Cs-10Ru/MPC-18 catalyst with high activity, fast responsibility and good stability has potential application in intermittently variable ammonia synthesis using CO2-free hydrogen derived from electrolysis of water using renewable energy with fast variability

Energy Efficient and Intermittently Variable Ammonia Synthesis over Mesoporous Carbon-Supported Cs-Ru Nanocatalysts

The Cs-promoted Ru nanocatalysts supported on mesoporous carbon materials (denoted as Cs-Ru/MPC) and microporous activated carbon materials (denoted as Cs-Ru/AC) were prepared for the sustainable synthesis of ammonia under mild reaction conditions (<500 °C, 1 MPa). Both Ru and Cs species were homogeneously impregnated into the mesostructures of three commercial available mesoporous carbon materials annealed at 1500, 1800 and 2100 °C (termed MPC-15, MPC-18 and MPC-21, respectively), resulting in a series of Cs-Ru/MPC catalysts with Ru loadings of 2.5−10 wt % and a fixed Cs loading of 33 wt %, corresponding to Cs/Ru molar ratios of 2.5−10. However, the Ru and Cs species are larger than the pore mouths of microporous activated carbon (shortly termed AC) and, as a consequence, were mostly aggregated on the outer surface of the Cs-Ru/AC catalysts. The Cs-Ru/MPC catalysts are superior to the Cs-Ru/AC catalyst in catalysing mild ammonia synthesis, especially for the 2.5Cs-10Ru/MPC-18 catalyst with a Ru loading of 10 wt % and a Cs/Ru ratio of 2.5, which exhibited the highest activity across a wide SV range. It also showed an excellent response and stability during cycling tests over a severe temperature jump in a short time, presumably due to the open mesoporous carbon framework and suitable surface concentrations of CsOH and metallic Ru species at the catalytically active sites. This 2.5Cs-10Ru/MPC-18 catalyst with high activity, fast responsibility and good stability has potential application in intermittently variable ammonia synthesis using CO2-free hydrogen derived from electrolysis of water using renewable energy with fast variability

Mild Ammonia Synthesis over Ba-Promoted Ru/MPC Catalysts: Effects of the Ba/Ru Ratio and the Mesoporous Structure

A series of novel mesoporous carbon-supported, Ba-promoted, Ru catalysts with Ba/Ru ratios of 0.1−1.6 and a Ru loading of 10 wt% (denoted as 0.1−1.6Ba-10Ru/MPC) were prepared via stepwise impregnation of Ru and Ba precursors on the mesoporous carbon materials. The catalysts were applied to mild ammonia synthesis and compared to reference materials, including an analog of the prepared catalyst with a Ba/Ru ratio of 1.6 and a Ru loading of 10 wt% (denoted as 1.6Ba-10Ru/AC). Characterization by X-ray diffraction (XRD), nitrogen physisorption, and electronic microscopy revealed that the 0.1−1.6Ba-10Ru/MPC catalysts contained Ru particles (approximately 2 nm) that were well-dispersed on the mesoporous structure and nanostructured Ba(NO3)2 species. These species decomposed into amorphous BaOx species, acting as a promoter on the metallic Ru particles forming catalytically active sites for ammonia synthesis. All the 0.1−1.6Ba-10Ru/MPC catalysts showed a synergistic effect of the active Ba and Ru species, which were stabilized in the mesoporous carbon framework with fast molecular diffusion and could effectively catalyze mild ammonia synthesis (280−450 °C and 0.99 MPa) even under intermittently variable conditions, particularly for those with Ba/Ru ratios of >0.5. In contrast, the 1.6Ba-10Ru/AC analog showed poor activity and stability for ammonia synthesis due to the sintering of Ba and Ru particles on the outer surface of the microporous carbon framework, resulting in low molecular diffusion and weak synergistic effect of the catalytically active sites

Mechanism of Lipid Radical Formation Following Exposure of Epidermal Homogenate to Ultraviolet Light

It has been suggested that oxygen free radicals are important mediators of lipid peroxidation in the epidermis exposed to ultraviolet (UV) light. However, it is not clear whether it is the superoxide anion radical (O2-) or the hydroxyl radial (.OH) that plays the major role in producing the lipid radical (L.) following UV exposure. In this study, we used electron spin resonance (ESR) technique with the spin trap (5,5-dimethyl-1-pyrroline-N-oxide [DMPO]) to determine which active oxygen species is involved in the UV -induced lipid radical formation (DMPO-L.: aN = 15.5 G, aH = 22.7 G). In the presence of superoxide dismutase or the metal-chelating agent, the DMPO-spin adduct spectrum of lipid radicals was reduced remarkably. The lipid radicals were formed by the hydroxyl radical generation system, not the superoxide anion generation system. The hydroxyl radical was found to be the direct active oxygen species that can generate lipid radicals as a result of .OH-mediated hydrogen atom abstraction. Superoixde anion radical stimulated the generation of hydroxyl radical via the iron-catalyzed reaction

Characteristics of carbonate beach materials in Okinoerabu Island and southern part of Okinawa main island

Carbonate beaches has functions as shore protection and recreation zone to attract many tourists, thus the beaches should be properly sustained. This paper mainly deals with the character for carbonate beach materials such as grain size distribution of carbonate natural beach material and nourished beach material in Okinawa and Okinoerbu islands, because the origin and source of beach sediment should be identified to protect a carbonate beach. The study shows that most of beach material is originated and around a coral reef, thus a coral reef system should be preserved to supply the sediment on the beach

Involvement of Active Oxygen in Lipid Peroxide Radical Reaction of Epidermal Homogenate Following Ultraviolet Light Exposure

To elucidate the radical mechanism of lipid peroxidation induced by ultraviolet light (UV) irradiation, an electron spin resonance (ESR) study was made on epidermal homogenate prepared from albino rat skin. The exposure of the homogenate to UV light resulted in an increase in lipid peroxide content, which was proportional to the time of UV exposure. Using ESR spin trapping (dimethyl-1-pyrroline-N-oxide, DMPO), the DMPO spin adduct spectrum of lipid radicals (L·) was measured following UV exposure (DMPO- L· :aN = 15.5 G, aH ≈ 22.7 G), as was the spectrum of DMPO-hydroxyl radical (DMPO-OH, aN = aH = 15.5 G). In the presence of superoxide dismutase, the DMPO spin adduct spectrum of lipid radicals was found to be reduced remarkably. Therefore, it was shown that the generation of the lipid radicals partially involves superoxide anion radicals, in addition to hydroxyl radicals. In the ESR free-radical experiment, an ESR signal appeared at g = 2.0064 when the ESR tube filled with homogenate was exposed to UV light at-150°C. The temperature-dependent change in the ESR free radical signal of homogenate exposed to UV light was observed at temperatures varying from-150°C to room temperature. By using degassed samples, it was confirmed that oxygen is involved in the formation of the lipid peroxide radicals (LOO·) from the lipid radicals (L·)

Field study of the generation of high speed reef current during winter season

Coral reef and carbonate beach attract many tourists for instance, nearly six million people in Okinawa. However, drowning accidents by a strong offshore current happen every year. Therefore, this paper deals with the physical characteristics of a reef current during winter season at Yoshiwara beach, Ishigakijima, Okinawa Prefecture, Japan, where drowning accidents were occurred by strong reef current during marine leisure activities. Field study on reef current was conducted in November and December, 2006 when northern wind prevailed the study area. The field study shows that the maximum 20-min average offshore velocity could be order of 2 m/s especially during winter season, because the northern wind that is perpendicular to the coast is persistent and generates reasonably high waves