• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3005-3012
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• 2013

The effect of Mn-promotion on high surface area Al-pillared montmorillonite (AlMMT) supported Co nanoparticles prepared by hydrothermal method have been investigated. A series of different weight% Mn-promoted Co nanoparticles were prepared and characterized by XRD, TPR, TGA, BET and SEM techniques. An increase in the surface area of MMT is observed with Al-pillaring. Fischer-Tropsch catalytic activity of the as prepared catalysts was studied in a fixed bed micro reactor at $225^{\circ}C$, $H_2/CO$ = 2 and at 1 atm pressure. The data showed that by the addition of Mn the selectivity of $C_1$ dropped drastically while that of $C_2-C_{12}$ hydrocarbons increased significantly over all the Mn-promoted Co/AlMMT catalysts. The $C_{13}-C_{20}$ hydrocarbons remained almost same for all the catalysts while the selectivity of $C_{21+}$ long chain hydrocarbons decreased considerably with the addition of Mn. The catalyst with 3.5%Mn showed lowest $C_{21+}$ and highest $C_2-C_{12}$ hydrocarbons selectivity due to cracking of long chain hydrocarbons over acidic sites of MMT.

• Korean Journal of Materials Research
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• v.33 no.2
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• pp.29-46
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• 2023

The electrochemical reduction of carbon dioxide (CO₂) to value-added products is a remarkable approach for mitigating CO₂ emissions caused by the excessive consumption of fossil fuels. However, achieving the electrocatalytic reduction of CO₂ still faces some bottlenecks, including the large overpotential, undesirable selectivity, and slow electron transfer kinetics. Various electrocatalysts including metals, metals oxides, alloys, and single-atom catalysts have been widely researched to suppress HER performance, reduce overpotential and enhance the selectivity of CO₂RR over the last few decades. Among them, single-atom catalysts (SACs) have attracted a great deal of interest because of their advantages over traditional electrocatalysts such as maximized atomic utilization, tunable coordination environments and unique electronic structures. Herein, we discuss the mechanisms involved in the electroreduction of CO₂ to carbon monoxide (CO) and the fundamental concepts related to electrocatalysis. Then, we present an overview of recent advances in the design of high-performance noble and non-noble singleatom catalysts for the CO₂ reduction reaction.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.215-223
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• 2005

Non-thermal plasma decomposition of gas-phase styrene was investigated in this study using three different types of plasma reactors; dielectric-barrier discharge (DBD) reactor, surface discharge (SD) reactor and plasma-driven catalyst (PDC) reactor packed with 2.0 wt% $Ag/TiO_2$ catalysts. The main parameters used for the comparative assessment of the plasma reactors include the decomposition efficiency, carbon balance, byproduct distribution, COx ($CO+CO_2$) selectivity and COx yield. The SD and the DBD reactors showed better conversion efficiency of styrene than that of the PDC reactor due to their larger capability in ozone formation. On the other hand, the PDC reactor showed better carbon balance, the yield and the selectivity of COx. The required specific input energies to achieve 100% carbon balance from the decomposition of 100 ppmv styrene using the plasma alone reactors and the PDC reactor were 420 J/L and 110 J/L, respectively. The major decomposition products in gas-phase were CO, $CO_2$ and HCOOH regardless of the types of plasma reactors. In the case of SD and DBD reactors, the $CO_2$ selectivity ranged in $39.5{\sim}60%$. The $CO_2$ selectivity in the PDC reactor was in range of $68.5{\sim}75.5%$.

• Journal of the Korean Applied Science and Technology
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• v.13 no.1
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• pp.67-74
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• 1996

This study was conducted to find a catalyst system which has high conversion and selectivity for the oxidative coupling of methane to produce ethane and ethylene. Various catalysts were tested in a fixed bed reactor ar $750^{\circ}C$, 1 atm, and the feed ratio($CH_4/O_2$) of 2/1. Under the reaction condition, 10wt%$PbSO_4/MgO$ catalyst showed the highest catalytic activity : methane conversion, $C_2$ selectivity and yield were 50, 40 and 20%, respectively. Catalysts containing sulfate compounds, 10wt%$PbSO_4/MgO$, 10wt%$MgSO_4/MgO$ and $Na_2SO_4/MgO$ revealed a moderate methane conversions such as 38, 50 and 50%, respectively and low $C_2$ selectivities such as 18, 5 and 9%, respectively. Catalysts containing carbonate compounds, 10wt%$PbCO_3/MgO$, 10wt%$Li_2CO_3/MgO$ and $NaCO_3/MgO$, also showed a moderate methane conversions such as 64, 44 and 51%, respectively and low $C_2$ selectivities such as 5, 6 and 2%, respectively. With the existence of chlorine and mercury, $C_2$ selectivity was decreased.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.156-163
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• 2018

High-performance mixed-matrix membranes that comprise both zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were synthesized with a solution casting technique to realize excellent $CO_2/CH_4$ separation. The incorporation of ZIF-8 nanocrystals alone in ODPA-TMPDA polyimide can be used to significantly enhance $CO_2$ permeability compared with that of pure ODPA-TMPDA. Meanwhile, the addition of a GO nanostack alone in ODPA-TMPDA contributes to improved $CO_2/CH_4$ selectivity. Hence, a composite membrane that contains both fillers displays significant enhancements in $CO_2$ permeability (up to 60%) and $CO_2/CH_4$ selectivity (up to 28%) compared with those of pure polymeric membrane. Furthermore, in contrast to the ZIF-8 mixed-matrix membrane, which showed decreased mechanical stability, it was found that the incorporation of GO could improve the mechanical strength of mixed-matrix membranes. Overall, the synergistic effects of the use of both fillers together are successfully demonstrated in this paper. Such significant improvements in the mixed-matrix membrane's $CO_2/CH_4$ separation performance and mechanical strength suggest a feasible and effective approach for potential biogas upgrading and natural gas purification.

• Journal of Hydrogen and New Energy
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• v.30 no.1
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• pp.14-20
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• 2019

The power to gas (P2G) is one of the energy storage technologies that can increase the storage period and storage capacity compared to the existing battery type. One of P2G technologies produces hydrogen by decomposing water from renewable energy (electricity) and the other produces $CH_4$ by reacting hydrogen with $CO_2$. The objective of this study is the reaction of $CO_2$ methanation which synthesized methane by reacting carbon dioxide and hydrogen. The effect of $CO_2$ conversion and $CH_4$ selectivity on reaction temperature, pressure, and methane contents over 40% Ni catalyst was mainly investigated throughout this study. As a result, the activity of this catalyst appeared to be the highest in $CH_4$ yield at around $400^{\circ}C$ and the selectivity of $CH_4$ increased with increasing reaction pressure. The methane content was not significantly influenced below 3% of all componets. As the space velocity increases from 10,000 to 30,000/hr, the $CO_2$ conversion rate tends to decrease.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.556-564
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• 2018

In this study, polyethylene oxide (PEO)/polyethylene-co-vinyl acetate (EVA)/multi-walled carbon nanotube (MWCNT)-COOH composite membranes were prepared by adding 1, 2, 3, and 5 wt% of MWCNT-COOH to PEO/EVA respectively. The gas permeation properties of $N_2$, $O_2$ and $CO_2$ at $30^{\circ}C$ and 4~8 bar pressure were investigated. In each PEO/EVA/MWCNT-COOH composite membranes, the permeability of $CO_2$ increased with increasing the pressure, but the permeability of $N_2$ and $O_2$ were independent of the feeding pressure. As the MWCNT-COOH content increased, the $CO_2$ permeability increased and then decreased above 2 wt% MWCNT-COOH content. The 2 wt% MWCNT-COOH composite membrane exhibited a $CO_2/N_2$ selectivity of 77.8 and a $CO_2$ permeability of 84 barrer at 8 bar. The high $CO_2/N_2$ selectivity and $CO_2$ permeability were due to the high affinity between the quadrupolar $CO_2$, polar ether groups of PEO, and the polar ester groups of EVA. Additionally, the strong affinity between $CO_2$ and the -COOH groups on the MWCNT surface contributed to the high permeability of $CO_2$.

• Membrane Journal
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• v.33 no.1
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• pp.23-33
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• 2023

In this study, a mixed matrix membrane was prepared by varying the contents of PEI-GO@ZIF-8 synthesized in PEBAX 2533, and the permeation characteristics of N₂ and CO₂ were studied. The N₂ permeability of the PEBAX/PEIGO@ZIF-8 mixed matrix membrane decreased as the PEI-GO@ZIF-8 content increased, and the CO₂ permeability showed different trends depending on the PEI-GO@ZIF-8 content. The CO₂ permeability increased in pure PEBAX membrane up to PEBAX/PEI-GO@ZIF-8 0.1 wt%, but decreased at the subsequent content. The PEI-GO@ZIF-8 0.1 wt% mixed matrix membrane had a CO₂ permeability of 221.9 Barrer and a CO₂/N₂ selectivity of 60.0, showing the highest permeation properties with improved CO₂ permeability and CO₂/N₂ selectivity among the prepared mixed matrix membrane and we obtained a result that reached the Robeson upper-bound. This is due to the -COOH, -O-, and -OH functional groups of GO and the amine group bonded to PEI, which interact friendly with CO₂, and the effect of ZIF-8, which causes gate-opening for CO₂ while the fillers are evenly dispersed in PEBAX.

• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Membrane Journal
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• v.27 no.2
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• pp.147-153
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• 2017

In this study, we investigated permeation properties of single gas ($N_2$, $O_2$, $CO_2$) through membranes composed of poly(ethylene oxide) (PEO) and poly(ethylene-co-vinyl acetate) (EVA) blend. The prepared membranes showed no new absorbance peaks, which indicate the physical blending of PEO and EVA by FT-IR analysis. SEM observation showed that the crystalline phase of PEO decreased with increasing EVA content in the PEO/EVA mixed matrix. DSC analysis showed that the crystallinity of the PEO/EVA blend membrane decreased with increasing EVA content. Gas permeation experiment was performed with various feed pressure (4~8 bar). The permeability increased in the following order: $N_2$ < $O_2$ < $CO_2$. The permeability of $CO_2$ in PEO/EVA blend membranes were increased with increasing feed pressure, However, the permeability of $N_2$ and $O_2$ were independent of feed pressure. On the other hand, the permeability of all the gases in PEO/EVA blend membranes increased with increasing amorphous EVA content in semi-crystalline PEO. In particular, the blend membrane with 40 wt% EVA showed $CO_2$ permeability of 64 Barrer and $CO_2/N_2$ ideal selectivity of 61.5. The high $CO_2$ permeability and $CO_2/N_2$ ideal selectivity are attributed to strong affinity between the polar ether groups of PEO or the polar ester groups of EVA and polar $CO_2$.