• Clean Technology
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• v.21 no.1
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• pp.68-75
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• 2015

In this study, we investigated the structure and properties of a highly heat conductive metal-ceramic core-shell CoAl₂O₄@Al micro-composite for heterogeneous catalysts support. The CoAl₂O₄@Al was prepared by hydrothermal surface oxidation of Al metal powder, which resulted in the structure with a high heat conductive Al metal core encapsulated by a high surface area CoAl₂O₄ shell. For comparison, CoAl₂O₄ was also prepared by co-precipitation method and also utilized for a catalyst support. Rh catalysts supported on CoAl₂O₄@Al and CoAl₂O₄ were prepared by incipient wetness impregnation and characterized by N₂ adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO chemisorption, and temperature-programmed reduction (TPR). The properties of catalysts were investigated for glycerol steam reforming reaction for hydrogen production at 550 ℃. Rh/CoAl₂O₄@Al exhibited about 2.8 times higher glycerol conversion turnover frequency (TOF) than Rh/CoAl₂O₄ due to facilitated heat transport through the core-shell structure. The CoAl₂O₄@Al and CoAl₂O₄ also showed some catalytic activities due to a partial reduction of Co on the support, and a higher catalytic activity was also found on the CoAl₂O₄@Al core-shell than CoAl₂O₄. These catalysts, however, displayed deactivation on the reaction stream due to carbon deposition on the catalysts surface.

• Journal of Acupuncture Research
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• v.25 no.5
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• pp.151-165
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• 2008

Objectives : To evaluate the effects of Head Acupuncture versus Upper and Lower Limbs Acupuncture on signal activation of Blood Oxygen Level Dependent(BOLD) fMRI on the Brain and Somatosensory Cortex. Subjects and Methods : 10 healthy normal right-handed female volunteer were recruited. The average age of the 10 subjects was 30 years old. The BOLD functional MRI(fMRI) signal characteristics were determined during tactile stimulation was conducted by rubbing 4 acu-points in the right upper and lower limbs($LI_1$, $LI_{10}$, $LV_3$, $ST_{36}$). After stimulation of Head Acupuncture in Sishencong($HN_1$), $GB_{18}$, $GB_9$, $TH_{20}$ of Left versus Upper and Lower Limbs Acupuncture($LI_1$, $LI_{10}$, $LV_3$, $ST_{36}$ of Right) and took off needles. Then the BOLD fMRI signal characteristics were determined at the same manner. Results : 1. When touched with cotton buds(sensory stimulation), left Parietal Lobe, Post-central Gyrus, primary somatosensory cortex(BA 1, 2, 3), and primary motor cortex(BA 4) were mainly activated. When $ST_{36}$ was stimulated, Frontal Lobe, Parietal Lobe, Cerebellum, and Posterior Lobe as well as Inter-Hemispheric displaying a variety of regions. 2. In signal activation before and after Head Acupuncture reaction, it showed signal activation after removing the acupuncture needle and right Somatosensory Association Cortex, Postcentral Gyrus, and Parietal Lobe were more activated. 3. In reactions of before and after Upper and Lower Limb Acupuncture, it also showed signal activation after removing the acupuncture needle and bilateral Occipital Lobe, Lingual Gyrus, visual association cortex, and Cerebellum were activated. 4. After acupuncture stimulation, In Upper and Lower Limb Acupuncture Group, left frontal Lobe, Precentral Gyrus and Bilateral parietal lobe, Postcentral Gyrus and Primary Somatosensory Cortex(BA 2) were activated. In Head Acupuncture Group, which has most similar activation regions, but especially right Pre-Post central Gyrus, Primary Somatosensory Cortex(BA 3), Primary Motor Cortex, frontal Lobe and Parietal Lobe were activated. Conclusions : When sensory stimulation was done with cotton buds on four acup-points($LI_1$, $LI_{10}4, $LV_3$, $ST_{36}$), while bilaterally activated, contralateral sense was more dominant. It showed consistency with cerebral cortex function. When $ST_{36}$ was stimulated Frontal Lobe, Parietal Lobe, Cerebellum, Posterior Lobe as well as Inter-Hemispheric were stimulated. In Head Acupuncture, it showed more contralateral activation after acupuncture. In Upper and Lower Limb Acupuncture, it showed typically contralateral activation and deactivation of limbic system after acupuncture stimulation. Therefore, there were different fMRI BOLD signal activation reaction before and after Head Acupuncture vs Upper and Lower Limb Acupuncture which might be thought to be caused by acu-points' sensitivity and different sensory receptor to response acupuncture stimulation.

• Clean Technology
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• v.20 no.2
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• pp.189-201
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• 2014

Partial oxidation, $CO_2$ reforming and the oxidative $CO_2$ reforming of $CH_4$ to produce synthesis gas over supported Ni hydrotalcite-type ($Ni_{0.5}Ca_{2.5}Al$ catalyst) catalysts were carried out and the effects of metal supports (i.e.; Mg and Ca) on the formation of a stable double-layer structure on the catalysts were evaluated. The $CH_4$ reforming stability was determined to be affected by the differences in the interaction strength between the active Ni ions and support metal ions. Only a Ni-Mg-Al composition produced a highly stable hydrotalcite-type double-layered structure; while the Ni-Ca-Al-type composition did not. Such structure provides excellent stability for the catalyst (-80% efficiency) as confirmed by the long-term $CO_2$ reforming test (-100 h), while the Ni-Ca-Al catalyst exhibited deactivation phases starting at the beginning of the reaction. The interaction strength between the active metal (Ni) and the supporting components (Mg and Al) was determined by temperature-programed reduction (TPR) analyses. The affinity was also confirmed by the TPR temperature because the Ni-Mg-Al catalyst required a higher temperature to reduce the Ni relative to the Ni-Ca-Al catalyst. The highest initial activity for synthesis gas production was observed for the $Ni_{0.5}Ca_{2.5}Al$ catalyst; however, this activity decreased quickly due to coke formation. The $Ni_{0.5}Ca_{2.5}Al$ catalyst exhibited a high reactivity and was more stable than the other catalysts because it had a higher resistance to coke formation.

• Clean Technology
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• v.25 no.1
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• pp.91-97
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• 2019

Oxidative desulfurization (ODS) has received much attention in recent years because refractory sulfur compounds such as dibenzothiophenes can be oxidized selectively to their corresponding sulfoxides and sulfones, and these products can be removed by extraction and adsorption. In this work, The oxidative desulfurization of marine diesel fuel was performed in a batch reactor with hydrogen peroxide ($H_2O_2$) in the presence of various supported heteropoly acid catalysts. The catalysts were characterized by XRD, XRF, XPS and nitrogen adsorption isotherm techniques. Based on the sulfur removal efficiency of promising silica supported heteropoly acid catalysts, the ranking of catalytic activity was: $30\;H_3PW_{12}/SiO_2$ > $30\;H_3PMo_{12}/SiO_2$ > $30\;H_4SiW_{12}/SiO_2$, which appears to be related with their intrinsic acid strength. The $30\;H_3PW_{12}/SiO_2$ catalyst showed the highest initial sulfur removal efficiency of about 66% under reaction conditions of $30^{\circ}C$, $0.025g\;mL^{-1}$ (cat./oil), 1 h reaction time. However, through the recycle test of the $H_3PW_{12}/SiO_2$ catalyst, significant deactivation was observed, which was attributed to the elution of the active component $H_3PW_{12}$. By introducing cesium cation ($Cs^+$) into the $H_3PW_{12}/SiO_2$ catalyst, the stability of the catalyst was improved with changing the solubility, and the $Cs^+$ ion exchanged catalyst could be recycled for at least five times without severe elution.

• Clean Technology
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• v.27 no.2
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• pp.198-204
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• 2021

This study focused on a two-step process using heterogeneous catalysts to produce biodiesel using Nepalese jatropha oil as a raw material. As a first step, the effect of the repetitive regeneration number of Amberlyst-15 on the esterification reaction of FFA in jatropha oil was investigated. Second, the possibility of a transesterification reaction scale-up using a dolomite bead catalyst was tested. Using 120 kg of jatropha seeds from Nepal, 30 L (27 kg) of jatropha oil was obtained, and the jatropha oil yield from the seeds was about 25.0 wt%. The acid value and FFA content of jatropha oil were measured to be 11.3 mgKOH g^-1 and 5.65%, respectively. As a result of the esterification reaction of jatropha oil using the Amberlyst-15 catalyst in the form of beads, the acid value of the reaction product could be lowered to 0.26 mgKOH g^-1 when the fresh Amberlyst-15 catalyst was used. As the regeneration of the Amberlyst-15 catalyst is repeated, the catalyst has been deactivated, and the esterification reaction performance has deteriorated. The cause of the deactivation seems to be due to the catalyst being broken and impurities being deposited. It was confirmed that the Amberlyst-15 catalyst could be reused up to 5 times for the esterification reaction of jatropha oil. In the second step, the transesterification reaction, a dolomite catalyst, was mass-produced and used in the form of beads. By transesterifying the pretreated jatropha oil in a spinning catalyst basket reactor equipped with 90 g of dolomite bead catalyst, 89.1 wt% of biodiesel yield was obtained in 2 hours after the start of the reaction, which was similar to the transesterification of soybean oil under the same conditions.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.407-417
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• 2020

The capacity of the designated landfill site for asbestos-containing waste is approaching its limit because the amount of asbestos-containing slate is increasing every year. There is a need for a method that can safely and inexpensively treat asbestos-containing slate in large capacity and at the same time recycle it. A cement kiln can be an alternative for heat treatment of asbestos-containing slate. We intend to develop a pilot scale device that can simulate the high temperature environment of a cement kiln using a high temperature plasma reactor in this study. In addition, this reactor can be used to inactivate asbestos in the slate and to synthesize one of the minerals of cement, to confirm the possibility of recycling as a cement raw material. The high-temperature plasma reactor as a pilot scale experimental apparatus was manufactured by downsizing to 1/50 the size of an actual cement kiln. The experimental conditions for the deactivation test of the asbestos-containing slate are the same as the firing time of the cement kiln, increasing the temperature to 200-2,000℃ at 100℃ intervals for 20 minutes. XRD, PLM, and TEM-EDS analyses were used to characterize mineralogical characteristics of the slate before and after treatment. It was confirmed that chrysotile [Mg3Si2O5(OH)4] and calcite (CaCO3) in the slate was transformed into forsterite (Mg2SiO4) and calcium silicate (Ca2SiO4), a cement constituent mineral, at 1,500℃ or higher. Therefore, this study may be suggested the economically and safely inactivating large capacity asbestos-containing slate using a cement kiln and the inactivated slate via heat treatment can be recycled as a cement raw material.

• Clean Technology
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• v.28 no.4
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• pp.269-277
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• 2022

With the recent development of the biological enzymatic reaction industry, lactic acid (LA) can be mass-produced from biomass sources. In particular, a catalytic process that converts LA into acrylic acid (AA) is receiving much attention because AA is used widely in the petrochemical industry as a monomer for superabsorbent polymers (SAP) and as an adhesive for displays. In the LA conversion process, NaY zeolites have been previously shown to be a high-activity catalyst, which improves AA selectivity and long-term stability. However, NaY zeolites suffer from fast deactivation due to severe coking. Therefore, the aim of this study is to modify the acid-base properties of the NaY zeolite to address this shortcoming. First, base promoters, Ca ions, were introduced to the NaY zeolites to tune their acidity and basicity via ion exchange (IE) and incipient wetness impregnation (IWI). The IWI method showed superior catalyst selectivity and stability compared to the IE method, maintaining a high AA yield of approximately 40% during the 16 h reaction. Based on the NH₃- and CO₂-TPD results, the calcium salts that impregnated into the NaY zeolites were proposed to exit as an oxide form mainly at the exterior surface of NaY and act as additional base sites to promote the dehydration of LA to AA. The NaY zeolites were further treated with KOH before calcium impregnation to reduce the total acidity and improve the dispersion of calcium through the mesopores formed by KOH-induced desilication. However, this KOH treatment did not lead to enhanced AA selectivity. Finally, calcium loading was increased from 1wt% to 5wt% to maximize the amount of base sites. The increased basicity improved the AA selectivity substantially to 65% at 100% conversion while maintaining high activity during a 24 h reaction. Our results suggest that controlling the basicity of the catalyst is key to obtaining high AA selectivity and high catalyst stability.