Eun-Hyeok Yang

Hydrogenation of CO2 to synthetic natural gas over supported nickel catalyst: effect of support on methane selectivity

Nickel-based catalysts were prepared by co-precipitation method and applied for the CO2 conversion to synthetic natural gas. Two batches of catalysts were prepared with the different amount of Ni and were characterized by various techniques such as XRD, TPD, TPR, XPS, and TEM. Catalytic activity was studied under atmospheric pressure, a temperature of 350xa0°C, GHSV of 2000xa0h−1 and N2:CO2:H2xa0=xa04:1:4. Highest CO2 conversion achieved was 70 with 99 % selectivity to methane. The activity of catalysts depends on the nickel content and nickel dispersion. Selectivity to methane depends inversely on the concentration of weak and moderate strength basic sites. Comparable quantity of basic sites present over catalysts, the methane selectivity is observed to be similar but the CO2 conversion changed due to change in Ni content. Catalysts having equal amounts of Ni exhibited increase in CH4 selectivity with the decrease in basic sites.

Synthesis of LaNiO3 perovskite using an EDTA-cellulose method and comparison with the conventional Pechini method: application to steam CO2 reforming of methane

LaNiO3 type perovskite was synthesized by two different methods, and characterized by various techniques such as in situ and ex situ XRD, TPR, N2 physisorption, CO chemisorption, TGA, FT-IR, XPS, TPH, TPSR and TEM-EDS. It was found that dried Pechini and EDTA precursors had different polymerization networks, and these dissimilar bonding and coordination states of each precursor led to differences in physicochemical properties after the calcination. Thus, differences in grain size of the perovskite and textural pores, which caused different nickel particle sizes and nickel particle dispersions after the reduction, were obtained for each catalyst. The calcined catalysts were applied to steam CO2 reforming of methane. It was found that the uniform particle size distribution, smaller nickel particle size and higher contact time for LaNiO3–EDTA brought a positive effect on the catalytic activity and stability with better resistance to carbon formation for steam CO2 reforming of methane.

Effect of cobalt supported on meso–macro porous hydrotalcite in Fischer–Tropsch synthesis

Hydrotalcite based cobalt catalysts were prepared by a slurry precipitation method, followed by a slurry impregnation method. The prepared supports and catalysts were characterized by N2 physisorption, mercury intrusion, chemisorption, TPR, TPD, SEM, TEM, TGA, DTA, and XRD techniques. Their catalytic performance for FTS was evaluated in a fixed-bed reactor with a H2/CO molar ratio of 2, reaction temperature of 240 °C, and reaction pressure of 25 bar. The incorporation of alumina and kaolin enlarged the inter void between hydrotalcite clusters, which resulted in macro porosity. The cobalt catalyst supported on a bimodal pore structure induced by kaolin showed a more stabilized catalytic activity and better heavy hydrocarbon selectivity in the FTS reaction when compared to other catalysts. The catalytic performance of the prepared catalyst depended on the cobalt reducibility and diffusion efficiency, which were determined by the cobalt particle size and porosity.

CO2 Reforming of Methane over Ni0/La2O3 Catalyst Without Reduction Step: Effect of Calcination Atmosphere

La-Ni precursor prepared by EDTA-cellulose method was calcined under different atmosphere (Air or Ar), and the catalysts were characterized by various techniques. In this study, the possibility of reduction free catalyst for dry reforming of methane was investigated as well. It was observed that LaNiO3 perovskite structure was formed under the calcination of Air atmosphere, while Ni0/La2O3-C structure was obtained under the calcination of Ar atmosphere due to the reducing and the oxidizing agents generated by the decomposition of organic species under inert atmosphere. It was found that even if LaNiO3-Ar had much larger size of nickel particle than LaNiO3-Air, the remained carbon species derived positive effect: the interfacial area among carbon, La2O3 and Ni0 could lead to synergetic sites such as basic sites, which enhanced resistance to carbon deposition. Furthermore, the higher CH4 activation energy and basicity of LaNiO3-Ar catalyst might ascribe to equilibrium between CH4 decomposition and CO2 gasification rates. Thus, it is suggested that remained carbon species in Ar calcined catalyst did not negatively affect the catalytic activity, but it affected stability positively.