• Transactions of the Korean hydrogen and new energy society
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• v.29 no.2
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• pp.170-180
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• 2018

After $MoS_2$ catalyst was prepared at 1, 30, and 70 atm, the hydrothermal pressure effect over preparation of $MoS_2$ was investigated in terms of catalyst characterization and direct methanation. Multifaceted characterization techniques such as XRD, BET, SEM, TPR, EDS, and XPS were used to analyze and investigate the effect of high pressure over the preparation of surface and bulk $MoS_2$ catalyst. Result from XRD, SEM, and BET demonstrated that $MoS_2$ was more dispersed as preparation pressure was increased, which resulted finer $MoS_2$ crystal size and higher surface area. EDS result confirmed that bulk composition was $MoS_2$ and XPS result showed that S/Mo mole ratio of surface was about 1.3. TPR showed that $MoS_2$ prepared at 30 atm possessed higher active surface sites than $MoS_2$ prepared at 1 atm and these sites could contribute to higher CO yield during methanation. Direct methanation was used to evaluate the CO conversion of the both catalysts prepared at 1 atm and 30 atm and reaction condition was at feed mole ratio of $H_2/CO=1$, GHSV=4800, 30 atm, temperature($^{\circ}C$) of 300, 350, 400, and 450. $MoS_2$ prepared at 30 atm showed more stable and higher CO conversion than $MoS_2$ prepared at 1 atm. Faster deactivation was occurred over $MoS_2$ prepared at 1 atm, which indicated that preparation pressure of $MoS_2$ catalyst was the dominant factor to improve the yield of direct methanation.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.419-428
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• 2020

The kinetics of direct methanation over activated charcoal-supported molybdenum catalyst at 30 bar was studied in a cylindrical fixed-bed reactor. When the temperature was not higher than 400℃, the CO conversion increased with increasing temperature according to the Arrhenius law of reaction kinetics. While XRD and Raman analysis showed that Mo was present as Mo oxides after reduction or methanation, TEM and XPS analysis showed that Mo₂C was formed after methanation depending on the loading of Mo precursor. When the temperature was as high as 500℃, the CO conversion was dependent not only on the Arrhenius law but also on the catalyzed reaction by nanoparticles, which came off from the reactor and thermocouple by metal dusting. These nanoparticles were made of Ni, Fe, Cr and alloy, and attributed to the formation of carbon deposit on the wall of the reactor and on the surface of the thermocouple. The carbon deposit consisted of amorphous and disordered carbon filaments.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.631-635
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• 2006

To investigate the characteristics of substitute natural gas (SNG) production from direct coal methanation, the continuous lab-scale entrained flow hydrogasifier (I.D. : 0.025 m, Height : 1.0 m) was used in this experiment. The hydrogasification system consisted of high pressure gas handling system, high pressure coal feeder, entrained flow hydrogasifier, and unreacted char separator. The experiment was performed at the various conditions of reaction temperature ($600{\sim}800^{\circ}C$), $H_2$/coal ratio (0.2~0.4), and coal feed rate (0.8~2.5 g/min). Although it was shown that carbon conversion was different trends with coals from the methanation results for 6 sample coals, the carbon conversion increased with increasing reaction temperature. And it increased with increasing H2/coal ratio, whereas the concentration of CH4 decreased. Also. the carbon conversion increased with the carbon content of coal sample and had a maximum value at volatile matter content of 35 wt％.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.443-454
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• 2013

Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically $V^{5+}$, $Co^{2+}$, and $Ni^{2+}$-incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated.