• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1092-1099
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• 2022

Research on exhaust aftertreatment devices to reduce air pollutants and greenhouse gas emissions is being actively conducted. However, in the case of the particulate matters/nitrogen oxides (PM/NOx) simultaneous reduction device for ships, the problem of back pressure on the diesel engine and replacement of the filter carrier is occurring. In this study, for the optimal design of the integrated device that can simultaneously reduce PM/NOx, an appropriate standard was presented by studying the flow inside the device and change in back pressure through the inlet/outlet pressure. Ansys Fluent was used to apply porous media conditions to a diesel particulate filter (DPF) and selective catalytic reduction (SCR) by setting porosity to 30%, 40%, 50%, 60%, and 70%. In addition, the ef ect on back pressure was analyzed by applying the inlet velocity according to the engine load to 7.4 m/s, 10.3 m/s, 13.1 m/s, and 26.2 m/s as boundary conditions. As a result of a computational fluid dynamics analysis, the rate of change for back pressure by changing the inlet velocity was greater than when inlet temperature was changed, and the maximum rate of change was 27.4 mbar. This was evaluated as a suitable device for ships of 1800kW because the back pressure in all boundary conditions did not exceed the classification standard of 68mbar.

• Clean Technology
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• v.28 no.3
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• pp.218-226
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• 2022

As a result of the recent social transformation towards a hydrogen economy and carbon-neutrality, the demands for hydrogen energy have been increasing rapidly worldwide. As such, eco-friendly hydrogen production technologies that do not produce carbon dioxide (CO₂) emissions are being focused on. Among them, ammonia (NH₃) is an economical hydrogen carrier that can easily produce hydrogen (H₂). In this study, Ru/Al₂O₃ catalyst coated onmetallic monolith for hydrogen production from ammonia was prepared by a dip-coating method using a catalyst slurry mixture composed of Ru/Al₂O₃ catalyst, inorganic binder (alumina sol) and organic binder (methyl cellulose). At the optimized 1:1:0.1 weight ratio of catalyst/inorganic binder/organic binder, the amount of catalyst coated on the metallic monolith after one cycle coating was about 61.6 g L^-1. The uniform thickness (about 42 ㎛) and crystal structure of the catalyst coated on the metallic monolith surface were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, a numerical optimization regression equation for NH3 conversion according to the independent variables of reaction temperature (400-600 ℃) and gas hourly space velocity (1,000-5,000 h^-1) was calculated by response surface methodology (RSM). This model indicated a determination coefficient (R²) of 0.991 and had statistically significant predictors. This regression model could contribute to the commercial process design of hydrogen production by ammonia decomposition.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.1-7
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• 2024

Mn-M/Al₂O₃ (M = Cu, Fe, Co, and Ce) catalysts were prepared for simultaneous oxidation of NO, CO, and CH₄, and their oxidation activities were compared. The Mn-Cu/ Al₂O₃ catalyst with the best simultaneous oxidation activity was characterized by XRD, Raman, XPS, and O₂-TPD analysis. The result of XRD indicated that Mn and Cu existed as complex oxides in the Mn-Cu/Al₂O₃ catalyst. Raman and XPS results showed that electron transfer between Mn ions and Cu ions occurred during the formation of the Mn-O-Cu bond in the Mn-Cu/Al₂O₃ catalyst. The XPS O 1s and O₂-TPD analyses showed that the Mn-Cu/Al₂O₃ catalyst has more adsorbed oxygen species with high mobility than the Mn/Al₂O₃ catalyst. The high simultaneous oxidation activity of the Mn-Cu/Al₂O₃ catalyst is attributed to these results. Gas-phase NO promotes the oxidation reactions of CO and CH₄ in the Mn-Cu/Al₂O₃ catalyst while suppressing the NO oxidation reaction. These results were presumed to be because the oxidized NO was used as an oxidizing agent for CO and CH₄. On the other hand, the oxidation reactions of CO and CH₄ competed on the Mn-Cu/Al₂O₃ catalyst, but the effect was not noticeable because the catalyst activation temperature was different.

• Applied Biological Chemistry
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• v.17 no.2
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• pp.125-137
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• 1974

The chemical structure of glycolipid of Selenomonas ruminantium cell wall was to be elucidated. The bacterial cells were treated in hot TCA and the glycolipid fractions were extracted by the solvent $CHCl_3\;:\;CH_3OH$ (1 : 3). The extracted glycolipids fraction was further separated by acetone extraction. The acetone soluble fraction was named as the spot A-compound. The acetone insoluble but ether soluble fraction was named as the spot B-compound. These two compounds were examined for elucidation of their chemical structure. The results were as follows: 1. The IR spectral analysis showed that O-acyl and N-acyl fatty acids were linked to glucosamine moiety in the spot A-compound. However in the spot B-compound in addition to O and N-acyl acids phosphorus was shown to be attached to glucosamine. 2. It was recognized by gas liquid chromatography that spot A compound contained beta-OH $C_{13:0}$ fatty acid in predominance in addition to the fatty acid with beta-OH $C_{9:0}$, whereas the spot B compound was composed of the predominant fatty acid of beta-OH $C_{13:0}$ with small amount of beta-OH $C_{9:0}$. 3. According to the paper chromatographic analysis of hydrazinolysis products of the spot A compound, a compound of a similar Rf value as the chitobiose was recognized, which indicated a structure of two molecules glucosamine condensed. The low Rf value of the hydrazinolysis product of the spot B-compound confirmed the presence of phosphorus attached to glucosamine. 4. The appearance of arabinose resulting from. ninhydrin decomposition of the acid hydrolyzate of the spot A compound indicated that the amino group is attached to $C_2$ of glucosamine. 5. The amount of glucosamine in the N-acetylated spot A compound decreased in half of the original content by the treatment. with $NaBH_4$, indicating that there are two molecules of glucosamines in the spot A compound. The presence of 1, 6-linkage between two molecules of glucosamine was suggested by the Morgan-Elson reaction and confirmed by the periodate decomposition test. 6. By the action of ${\beta}-N-acetyl$ glucosaminidase the N-acetylated spot A compound was completely decomposed into N-acetyl glucosamine, whereas the spot B compound was not. This indicated the spot A compound has a beta-linkage. 7. When phosphodiesterase or phosphomonoesterase acted on $^{32}P-labeled$ spot B compound, $^{32}P$ was not released by phosphodiesterase, but completely released by phosphomonoesterase. This indicated that one phosphorus is linked to glucosamine moiety. 8. The spot A compound is assumed to have the following chemical structure: That is glucosaminyl, ${\beta}-1$, 6-glucosamine to which O-acyl and N-acyl fatty acids are linked, of which the predominant fatty acid is beta-OH $C_{13:0}$ fatty acid in addition to beta-OH $C_{9:0}$ fatty acid 9. The spot B compound is likely to have the linkage of $glucosaminyl-{\beta}-1$, 6-glucosamine to which phosphorus is linked in monoester linkage. Furthermore both O-acyl and N-acyl fatty acids contained beta-OH $C_{13:0}$ fatty acid predominantly in addition to beta-OH $C_{9:0}$ fatty acid.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.853-860
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• 2012

To estimate potential use of fly ash in reducing $CH_4$ and $CO_2$ emission from soil, $CH_4$ and $CO_2$ fluxes from a paddy soil mixed with fly ash at different rate (w/w; 0, 5, and 10%) in the presence and absence of fertilizer N ($(NH_4)_2SO_4$) addition were investigated in a laboratory incubation for 60 days under changing water regime from wetting to drying via transition. The mean $CH_4$ flux during the entire incubation period ranged from 0.59 to $1.68mg\;CH_4\;m^{-2}day^{-1}$ with a lower rate in the soil treated with N fertilizer due to suppression of $CH_4$ production by $SO_4^{2-}$ that acts as an electron acceptor, leading to decreases in electron availability for methanogen. Fly ash application reduced $CH_4$ flux by 37.5 and 33.0% in soils without and with N addition, respectively, probably due to retardation of $CH_4$ diffusion through soil pores by addition of fine-textured fly ash. In addition, as fly ash has a potential for $CO_2$ removal via carbonation (formation of carbonate precipitates) that decreases $CO_2$ availability that is a substrate for $CO_2$ reduction reaction (one of $CH_4$ generation pathways) is likely to be another mechanisms of $CH_4$ flux reduction by fly ash. Meanwhile, the mean $CO_2$ flux during the entire incubation period was between 0.64 and $0.90g\;CO_2\;m^{-2}day^{-1}$, and that of N treated soil was lower than that without N addition. Because N addition is likely to increase soil respiration, it is not straightforward to explain the results. However, it may be possible that our experiment did not account for the substantial amount of $CO_2$ produced by heterotrophs that were activated by N addition in earlier period than the measurement was initiated. Fly ash application also lowered $CO_2$ flux by up to 20% in the soil mixed with fly ash at 10% through $CO_2$ removal by the carbonation. At the whole picture, fly ash application at 10% decreased global warming potential of emitted $CH_4$ and $CO_2$ by about 20%. Therefore, our results suggest that fly ash application can be a soil management practice to reduce green house gas emission from paddy soils. Further studies under field conditions with rice cultivation are necessary to verify our findings.