• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.95-102
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• 2023

Despite the easing of social distancing, demand for non-face-to-face services continues to rise. Recently, the EU is pursuing a comprehensive plastic use reduction by expanding the scope of plastic use regulations for packaging plastics according to the New Cyclical Economy Action Plan(NCEAP). In response to this trend, the packaging industry is moving away from conventional non-degradable/petroleum-based plastics and conducting research on packaging materials using biodegradable plastics such as PLA(Poly Lactic Acid), PBAT(Poly Butylene Adipate-co-butylene Terephthalate). On the other hand, ginkgo leaves occur in large quantities in Korea and act as a cause of slip accidents and flooding. In this study, a method to utilize ginkgo biloba leaf as a new alternative biomass resource was proposed by producing lactic acid through pretreatment, enzymatic saccharification, and fermentation processes. For the efficiency of lactic acid production, a comparative analysis of lignin content from before and after browning was performed. In addition, the degree of glucan extraction was evaluated by applying a pretreatment method using three catalysts: hot water, sulfuric acid, and sodium hydroxide. It is difficult to expect high production of lactic acid with single process. Therefore, an integrated process operation using both the pretreated hydrolyzate and the residual solid enzymatic saccharification solution must necessarily be applied.

• Clean Technology
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• v.15 no.4
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• pp.273-279
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• 2009

$SF_6$, which has a high global warming potential, can be decomposed to sulfur and fluorine compounds through hydrolysis by $H_2O$ or oxidation by $O_2$ over solid acid catalysts. In this study ${\gamma}-Al_2O_3$ was employed as the solid acid catalyst for the abatement of $SF_6$ and its catalytic activity was investigated with respect to the reaction temperature and the space velocity. The catalytic activity for $SF_6$ decomposition by the hydrolysis reached the maximum at and above 973 K with the space velocity of $20,000\;ml/g_{-cat}{\cdot}h$, exhibiting a conversion very close to 100%. When the space velocity was lower than $45,000\;ml/g_{-cat}{\cdot}h$, the conversion was maintained at the maximum value. On the other hand, the conversion of $SF_6$ by the oxidation was about 20% under the same conditions. The SEM and XRD analyses revealed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during the hydrolysis and to $AlF_3$ during the oxidation, respectively. The size of $AlF_3$ after the oxidation was over $20\;{\mu}m$, and its catalytic activity was low due to the low surface area. Therefore, it was concluded that the hydrolysis over ${\gamma}-Al_2O_3$ was much more favorable than the oxidation for the catalytic decomposition of $SF_6$.

• Clean Technology
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• v.16 no.4
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• pp.284-291
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• 2010

Nitrous oxide ($N_2O$) is a greenhouse material which is hard to remove. Even with a catalytic process it requires a reaction temperature, at least, higher than 670 K. This study has been performed to see the effects of Ce addition to the mixed oxide catalyst which shows the highest activity in decomposing $N_2O$ completely at temperature as low as 473 K when CO is used as a reducing agent. Mixed metal oxide(MMO) catalyst was made through co-precipitation process with small amount of Ce added to the base components of Co, Al and Rh or Pd. Consequently, the surface area of the catalyst decreased with the contents of Ce, and the catalytic activity of direct decomposition of $N_2O$ also decreased. However, in the presence of CO, the activity was found high enough to compensate the portion of activity decrease by Ce addition, so that it can be ascertained that the catalytic activity and stability can be maintained in the CO involved $N_2O$ reduction system when Ce is added for the physical stability of the catalyst.

• Resources Recycling
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• v.31 no.6
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• pp.25-35
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• 2022

The adsorption/desorption behavior and separation conditions of vanadium and tungsten ions were investigated using a gel-type anion-exchange resin. In the adsorption experiment with the initial acidity of the solution, the adsorption rate of vanadium was remarkably low in strong acids and bases. Additionally, the adsorption rate of tungsten was low in a strong base. An increase in the reaction temperature increased the adsorption reaction rate and maximum adsorption. The effect of tungsten on the maximum adsorption was minimal. The adsorption isotherms of vanadium and tungsten on the ion-exchange resin were suitable for the Langmuir adsorption isotherms of both the ions. For tungsten, the adsorption isotherms of vanadium and tungsten were polyoxometalate. Both ion-exchange resins were simulated using similar quadratic reaction rate models. Vanadium was desorbed in the aqueous solutions of HCl or NaOH, the desorption characteristics of vanadium and tungsten depended on the desorption solution, and tungsten was desorbed in the aqueous solution of NaOH. It was possible to separate the two ions using the desorption process. The desorption reaction reached equilibrium within 30 min, and more than 90% recovery was possible.

• Clean Technology
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• v.29 no.1
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• pp.46-52
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• 2023

Oxalic acid has been traditionally obtained via the oxidation of carbohydrates using nitric acid and catalysts. However, this process produces a variety of nitrogen oxides during oxidation and requires a separation process due to its various intermediates. These products and additional steps increase the harmfulness and complexity of the process. Recently, the electrochemical reduction of carbon dioxide into oxalic acid has been suggested as an environmentally friendly and efficient technology for the production of oxalic acid. In this electrochemical conversion system, zinc oxalate (ZnC₂O₄) is obtained by the reaction of Zn²⁺ ions produced by Zn oxidation and oxalate ions produced by CO₂ reduction. ZnC₂O₄ can then be converted to form oxalic acid, but this requires the use of a strong acid and heat. In this study, a system was proposed that can easily convert ZnC₂O₄ to oxalic acid without the use of a strong acid while also allowing for easy separation. In addition, this proposed system can also further convert the products into glycolic acid which is a high-value-added chemical. ZnC₂O₄ was effectively separated into Zn(OH)₂ powder and oxalate solution through a chemical treatment and a vacuum filtration process. Then the Zn(OH)₂ and oxalate were electrochemically converted to zinc and glycolic acid, respectively.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.175-188
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• 2023

Global interest in hydrogen energy is increasing as an eco-friendly future energy that can replace fossil fuels. Accordingly, a next-generation hydrogen production technology using microorganisms, nuclear power, etc. is being developed, while a lot of time and effort are still required to overcome the cost of hydrogen production based on fossil fuels. As a way to minimize greenhouse gas emissions in the hydrocarbon-based hydrogen production process, methane direct decomposition technology has recently attracted attention. In order to improve the economic feasibility of the process, the simultaneous production of value-added carbon materials with hydrogen can be one of the most essential aspects. For that purpose, various studies on catalysis related to the quality and yield of high-value carbon materials such as carbon nanotubes (CNTs). In terms of process technology, a number of the research and development of fluidized-bed reactors capable of continuous production and improved gas-solid contact efficiency has been attempted. Recently, methane direct decomposition technology using a fluidized bed has been developed to the extent that it can produce 270 kg/day of hydrogen and 1000 kg/day of carbon. Plus, with the development of catalyst regeneration, separation and recirculation technologies, the process efficiency can be further improved. This review paper investigates the recent development of catalysts and fluidized bed reactor for methane direct pyrolysis to identify the key challenges and opportunities.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.307-312
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• 2023

In this study, a catalytic oxidation-heat recovery system was designed that can remove unreacted with a concentration of about 1% to 6% in the exhaust gas of hydrogen fuel cells and recover heat to ensure safety in the hydrogen economy. The safety system was devised by filling hydrogen oxidation catalysts at room temperature that can remove unreacted hydrogen without any energy source, and an exhaust-heat recovery device was integrated to efficiently recover the heat released from the oxidation reaction. Through CFD analysis, variations in pressure and fluid within the system were shown depending on the filling conditions of the hydrogen oxidation system. In addition, it was found that waste heat could be recovered by optimizing the temperature of the exhaust gas, flow rate, and pressure conditions within the heat recovery system and securing hot water above 40 ℃ by utilizing the exhaust gas oxidation heat source above 300 ℃. Through this study, it was possible to confirm the potential of utilizing hydrogen processes, which are applied in small to medium-sized systems such as hydrogen fuel cells, as a safety system by evaluating them at a pilot scale. Additionally, it could be a safety guideline for responding to unexpected hydrogen safety accidents through further pilot-scale studies.

• Clean Technology
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• v.29 no.2
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• pp.79-86
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• 2023

The homogeneous catalyst, Ru-MACHO-BH, selectively performs hydrogenation reactions only on the carbonyl group of α, β-unsaturated aldehyde compounds with extremely high reactivity and selectivity. However, the hydrogenation of α, β-unsaturated aldehydes involves a heterogeneous Diels-Alder reaction, resulting in the formation of significant amounts of byproducts, such as dimers. In this study, we used the Ru-MACHO-BH catalyst (Carbonyl hydrido (tetrahydroborato) [bis (2-diphenyl phosphino ethyl) amino] ruthenium(II)) to selectively hydrogenate the carbonyl group of a specific type of α, β-unsaturated aldehyde called methacryl aldehyde, leading to the synthesis of methallyl alcohol. Simultaneously, we applied diols to inhibit the formation of byproducts. The results demonstrate that monoethylene glycol can significantly reduce the formation of diols. Based on these results, we effectively suppressed the formation of dimers containing vinyl groups in methacryl aldehyde by using hydroquinone, which can efficiently inhibit the chemical interaction of vinyl groups. Consequently, the conversion rate of methacryl aldehyde was increased. Ultimately, by reducing the amount of the expensive homogeneous catalyst Ru-MACHO-BH to 1/10, we achieved a selectivity of over 90% and a yield of over 80% for the desired product, methallyl alcohol. These results provide a method to minimize yield reduction while reducing the usage of expensive catalysts, thereby improving cost-effectiveness. We expect that the reaction could be applied to various kinds of selective hydrogenation and has been successfully run on an industrial scale.

• Asia Marketing Journal
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• v.14 no.3
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• pp.69-102
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• 2012

Owing to increased number of luxury brand users, both genuine and counterfeit luxury product consumption continues to increase every year. Luxury brand is defined as use or display of a particular branded products which brings the ownership prestige apart from its functional utility(Grossmand and Shapiro 1988). Some luxury brands have imitations sold in marketplace due to their popularity. These imitations or counterfeits have been jumping on the bandwagon of the upturn in sales of their originals. The purpose of our study is to understand consumer's underlying motives to consume luxury brands, genuine and or counterfeits. To do this, we propose functional theories of attitudes, decision-making styles, and life attitudes to form the determining causes for different consumption choices of luxury brands: genuine brands, counterfeit brands, both genuine and counterfeit brands, and no consumption on luxury brands types. In proposed causal pathways, we examine moderated effects of socio-psychological factors to further investigate if consumer profiles would exert influences in causal relationships. From the existing theories of functional attitudes: value-expressive and social-adjustive attitudes, we developed and introduced a new measure of rationality-consumptive attitude. From the existing eight decision-making characteristics of consumer styles inventory(CSI), three measures of high-quality, hedonic-shopping, and price-shopping styles were primarily applied in the study along with newly introduced measure of 'high-price' being added, which makes four total. Seven life attitude measures of life purpose, life control, will to meaning, goal seeking, future mean to fulfill, life satisfaction, and religiosity were applied. Finally, such socio-psychological measures as age, gender, marital status, income, and age-gap between couples were assumed to function as moderators. With 430 valid study samples, ages from 20s to 50s, with more females(316) than males(114), with average personal possessions of 5 genuine and 9 counterfeit luxury brands, we conducted questionnaire survey. Results indicated that social-adjustive function is totally disappeared in the relationship due to current social trend of widespread consumptions on both genuine and counterfeit brands which in turn, make consumers feel less special on wearing or carrying them unlike in the past. Self-expressive function and rationality-consumptive functions act as strong catalysts for genuine brand consumption and counterfeit brand consumption, respectively. On consumers' decision-making styles, high-price sublation is the most powerful indicator anticipating counterfeit consumption, even more powerful than personal incomes. In life attitude, the overall model fit was not validated, and only life control and life satisfaction are proven to be significant on both genuine and counterfeit product consumptions. Employment of socio-psychological factors in the model improved understanding of users further. Young consumers tend to go for genuine products over counterfeits. Consumers in different income groups; low, medium and high, all significantly consume genuine products for reasons of different decision-making styles. The results indicated that consumers whose personal disposition is predisposed to consume products in the form of reflection of his or her personality, go only for genuine brands for quality reason, while consumers who rationally consume products for its function or usability, go only for counterfeits for high-price sublation reason. Meanwhile, both product users support for high-price orientation who are not well off.