Min Hye Youn

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous nickel–alumina aerogel catalyst

Abstract A mesoporous nickel–phosphorus–alumina aerogel catalyst (NPAA) was prepared by a single-step epoxide-driven sol–gel method and a subsequent supercritical CO2 drying method for use in the hydrogen production by steam reforming of liquefied natural gas (LNG). In order to investigate the effect of drying method of nickel–phosphorus–alumina catalysts on their physicochemical properties and catalytic activities, a mesoporous nickel–phosphorus–alumina xerogel catalyst (NPAX) was also prepared by a single-step epoxide-driven sol–gel method and a subsequent evaporative drying method for comparison purpose. It was found that supercritical CO2 drying method was effective for enhancing textural properties of NPAA catalyst. Although both NPAX and NPAA catalysts retained surface nickel aluminate phase, NPAA catalyst showed stronger metal-support interaction than NPAX catalyst. XRD patterns of reduced NPAX and NPAA catalysts revealed that NPAA catalyst retained smaller metallic nickel crystallite than NPAX catalysts. It was also observed that the reduced NPAA catalyst exhibited high nickel dispersion, large amount of strong hydrogen-binding sites, and large amount of methane adsorption compared to the reduced NPAX catalyst. In the steam reforming of LNG, NPAA catalyst with high affinity toward methane showed a better catalytic performance than NPAX catalyst.

Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide by Heteropolyacid/Metal Oxide Catalysts

CexTi1-xO2 and H3PW12O40/CexTi1-xO2 catalysts were prepared by sol-gel method, and they were applied to the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide in a batch reactor. The reaction was carried out in an autoclave reactor at 170oC and 5 MPa. It was found that CexTi1-xO2 exhibited a higher catalytic performance than pure CeO2 and TiO2. The catalytic performance of CexTi1-xO2 was the maximum when x=0.1. It was also revealed that H3PW12O40/CexTi1-xO2 catalysts showed a remarkably enhanced catalytic performance than the corresponding CexTi1-xO2 catalysts. The amount of DMC produced by 15 wt% H3PW12O40/ Ce0.1Ti0.9O2 catalyst was six times higher than that produced by Ce0.1Ti0.9O2 catalyst. It is concluded that both Brönsted acid sites provided by H3PW12O40 and base sites in CexTi1-xO2 played an important role in improving the catalytic performance of H3PW12O40/CexTi1-xO2.

The salt-based catalytic enhancement of CO2 absorption by a tertiary amine medium

The rise in atmospheric CO2 levels due to the effects of human activities poses a serious threat to the worlds ecosystems because of global warming and climate change. Efficient methods are needed to limit the elevation of CO2 levels in the atmosphere. Here, we propose an improved CO2 sequestration method that uses new catalysts, specifically a series of tertiary amine nitrate salts, in an aqueous tertiary amine medium. We synthesized the new catalysts and characterized them by using 1H and 13C NMR, single crystal X-ray analysis, and FT-IR spectroscopy. The effects of the catalysts on CO2 absorption were assessed by using a stopped-flow spectrophotometer, and their heats of absorption and CO2 absorption capacities were measured with a differential reaction calorimeter (DRC) at high concentrations of the tertiary amine medium. The CO2 hydration rate constants were determined under basic conditions and the catalysts were found to exhibit higher absorption of CO2 (a highest value of 430 M−1 s−1) than the tertiary amine medium (133 M−1 s−1). The increased absorption of CO2 and the low heat absorption energies of the new catalysts suggest that they could be used in post-combustion processes.

Catholyte‐Free Electrocatalytic CO2 Reduction to Formate

Electrochemical reduction of carbon dioxide (CO2 ) into value-added chemicals is a promising strategy to reduce CO2 emission and mitigate climate change. One of the most serious problems in electrocatalytic CO2 reduction (CO2 R) is the low solubility of CO2 in an aqueous electrolyte, which significantly limits the cathodic reaction rate. This paper proposes a facile method of catholyte-free electrocatalytic CO2 reduction to avoid the solubility limitation using commercial tin nanoparticles as a cathode catalyst. Interestingly, as the reaction temperature rises from 303 K to 363 K, the partial current density (PCD) of formate improves more than two times with 52.9 mA cm-2 , despite the decrease in CO2 solubility. Furthermore, a significantly high formate concentration of 41.5 g L-1 is obtained as a one-path product at 343 K with high PCD (51.7 mA cm-2 ) and high Faradaic efficiency (93.3 %) via continuous operation in a full flow cell at a low cell voltage of 2.2 V.

Enhancement of carbon dioxide absorption rate with metal nano particles

With increasing concern about global warming, CCS (Carbon dioxide capture and storage) has attracted much attention as a promising technology for reducing CO2 emission. It is necessary to develop the cost-effective absorbents materials in order to rapid commercialize CCS technologies. In this work, he study for the promotion of absorption rate in CO2 capture system using metal nanoparticle were investigated. Three kinds of metal nanoparticle, cobalt, zinc, and nickel, were prepared by wet and dry method and effect of preparation method on the absorption rate of CO2 were compared. Among the tested using pH method, nickel nanoparticle prepared by wet method showed the most significant improvement of CO2 absorption rate. In case that metal nanoparticle is applied to CCS process, it is expected to be more efficient in CO2 capture process due to reduce the size of absorption tower.

Microporous and mesoporous ZSM-5 catalyst for catalytic cracking of C5 raffinate to light olefins.

ZSM5 catalysts (PAM(X)-ZSM5) with micropores and mesopores were prepared using polyacrylamide (PAM) as a soft template at different PAM content (X = 0, 0.12, 0.25, 0.53, 0.64, and 0.78 wt%), and they were applied to the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of PAM content of PAM(X)-ZSM5 catalysts on the physicochemical properties and catalytic activities was investigated. N2 adsorption-desorption isotherms of PAM(X)-ZSM5 catalysts exhibited a broad hysteresis loop at high relative pressure, indicating the existence of mesopores in the catalysts. It was found that the catalytic performance of PAM(X)-ZSM5 catalysts was closely related to the mesoporosity of the catalysts. Conversion of C5 raffinate and yield for light olefins showed volcano-shaped trends with respect to mesopore/micropore volume ratio of the catalysts. Thus, an optimal PAM content was required to achieve maximum production of light olefins through catalytic cracking of C5 raffinate over microporous and mesoporous PAM(X)-ZSM5 catalysts.