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The Fe/CeO2 catalyst showed a high activity for reverse water gas shift (RWGS) reaction. Almost no loss of RWGS activity on Fe/CeO2 catalysts even in reaction atmospheres containing high concentrations of hydrogen sulfide.

The 2,5-dimethyl-1-hexene could be produced by dimerization of isobutene in the presence of hydrogen sulfide due to the generation of SH radicals.

In this study, hydrogen and carbon nanotubes (CNTs) are simultaneously produced via a synergistic combined process of CO2 methanation (METH) and chemical vapor deposition (CVD) processes using biogas as a feedstock. METH process could upgrade CO2 containing biogas into CH4-rich gas which then decomposed into H2 and forming CNTs over CoMo/MgO catalyst by CVD process. The effects of Ce addition to CoMo/MgO were investigated. Comprehensive characterization confirms that all as-synthesized samples composed of well-aligned multi-walled carbon nanotubes (MWCNTs) with a narrow size distribution. The Ce addition improved CoMo dispersion on MgO, resulting in smaller and uniform CNTs. The small addition of Ce into CoMo/MgO catalyst could enhance the production CNTs yield. The higher Ce addition would, however, result in the CNTs yield decreased, attributed to a high basicity of CeO2 surface and a large coverage of CeO2 on the catalyst surface. The IG/ID increased with increased Ce addition, while the surface area monotonically decreased, attributed to a decrease in defects of nanotubes. In addition, this wisely combined process could result in a remarkable 100%CO2 elimination, while high CH4 conversion of 90% was obtained. The H2 production yield could gain more than 30 vol% with respect to H2 in the feed stream. The H2 yield and purity in the effluent gas stream were approximately 90%.

In this study, a series of Ni catalysts supported on CeO2 with different morphologies including nanopolyhedrons (PH), nanorods (NR), nanoparticles (NP) and nanocubes (NC) was prepared via hydrothermal / wet impregnation method. The catalytic performance of as-prepared catalysts was evaluated for low-temperature CO2 methanation. The Ni/CeO2 catalysts exhibited a superior CO2 conversion and CH4 selectivity over METH®134, a commercial methanation catalyst. The following order of activity was experimentally found : Ni/CeO2-PH > Ni/CeO2-NR > Ni/CeO2-NP > Ni/CeO2-NC > METH®134. Among different CeO2 morphologies, the Ni/CeO2-NR catalyst exhibited the largest surface area and the highest reducibility, providing the high oxygen vacancies/oxygen storage capacity (OSC). Nevertheless, the strong metal-support interaction (SMSI) between Ni and Ce of the Ni/CeO2-NR catalyst determined by H2-TPR posed a negative impact on the CO2 conversion at low temperature. Unexpectedly, the Ni/CeO2-PH catalyst possessed a single crystalline CeO2 nanostructure of ca. 7.4 nm with relatively high surface area and high reducibility especially at low reduction temperature. Therefore, the Ni/CeO2-PH catalyst was found to be the optimum catalyst for low-temperature CO2 methanation.

In thid study, Ni/CeO2 catalysts were prepared by a one-step co-precipitation of nickel and cerium salts in a NaOH solution treated by different heating methods including microwave (MW), hydrothermal (HM) and evaporation (EP). With TEM observation, the co-precipitation provided the catalysts containing a highly crystalline CeO2 of a (111) plane structure with d-spacing of 3.15–3.24 A. The obtained CeO2 nanoparticles exhibited a pseudo-spherical shape with a size range of 10.8–12.1 nm. Based on HR-TEM analyses, NiO nanoparticles with a large size range of 48.8–51.2 nm were found to be incorporated within the CeO2 nanostructure. By N2 sorption measurement, all Ni/CeO2 catalysts possessed a mesoporous characteristic with a specific surface area range of 70.5–75.7 m2/g and an average pore diameter of 30 nm. XRD results revealed that NiO species could be completely transformed into Ni0 species by the H2 reduction process. XPS analyses further confirmed the presence of Ni0 species with a prominent peak at an energy bandgap of 852.6 eV. Hydrogen temperature-programmed reduction (H2-TPR) confirmed that α and β peaks of NiO species were completely reduced at a temperature lower than 500 °C. The Ni/CeO2 catalyst prepared by MW method exhibited a higher strong metal-support interaction (SMSI) between Ni and CeO2 revealed by H2 consumption results. The Ni/CeO2 catalysts prepared by MW, HM, EP methods exhibited the CO2 methanation activity with TOF of 13.6, 10.8 and 5.8 s−1, which could be correlated with the Ni crystallite sizes of 42.2, 50.5 and 52.8 nm, respectively. All prepared Ni/CeO2 catalysts exhibited the stable catalytic performances with a negligible drop in CO2 conversion and CH4 selectivity over 72 h-time-on-stream test. In comparison, the MW method with a rapid and uniform heating under autogenous pressure could result in the Ni/CeO2 catalyst with the superior catalytic activities due to the higher dispersion of Ni.

Selecting a suitable catalyst for implementing both simultaneous productions of hydrogen-rich syngas and multi-walled carbon nanotubes (MWCNTs) through the integration of dry reforming and methane decomposition reactions has recently gained great interests. In this study, a series of bimetallic (NiMo/MgO) and trimetallic (CoNiMo/MgO, FeNiMo/MgO, CoFeMo/MgO) catalysts was prepared and evaluated for a catalytic activity of CH4 and CO2 conversions of biogas in a fixed bed reactor at 800°C and atmospheric pressure. Among the catalysts investigated for directly converting biogas process, the bimetallic NiMo/MgO catalyst showed the outstanding catalytic performance with 86.4% CH4 conversion and 95.6% CO2 conversion as well as producing the highest syngas purity of 90.0% with H2/CO ratio = 1.1. Moreover, the characterization of the synthesized CNTs proved that the well-aligned structured morphology, high purity, and excellent textural properties were obtained using NiMo/MgO catalyst. On the other hand, using trimetallic catalysts which have the composition of Co and Fe particles leads to severe deactivation. This could be elucidated by the influence of the catalyst oxidation with CO2 in biogas, resulting in the transformation of metal into large metal oxide. The integrative process through using NiMo/MgO catalysts is regarded as a promising pathway, which has potentially useful for directly converting biogas into a high value-added product and provides a management approach for the enormous amounts of wastes.

Recently, NiSx based catalysts are promising electrocatalysts for Hydrogen Evolution Reaction (HER) via water electrolysis. In particular, the S/Ni ratio is crucial to improve catalytic activity of NiSx based catalysts. Herein, we synthesized NiSx based catalysts (Ni/S/C) with a tuned S/Ni molar ratio using Ni2+ ions exchange resin. We succeeded in synthesizing Ni/S/C with different S/Ni molar ratio in the range of 0.33–1.72 by changing Ni2+ ions exchange degree. The combination of NiSx and conductive carbon support contributes to high catalytic activity of Ni/S/C on HER. Additionally, Ni/S/C with the S/Ni molar ratio of 0.6 showed the highest onset potential; Ni3S2 is the most active catalyst for HER in NiSx species. Our synthesis method can easily tune the ratio of S/transition metal. This work provides a new direction for the catalyst design of transition metal sulfides and expands their utilization in sustainable catalytic reaction processes.

The methanation performance of a Ni/CeO2 structured catalyst having a spiral shape was investigated using a feed material gas containing 1–11 vol % oxygen. The spiral catalyst exhibited high methan...

CO2 methanation over a Ni/CeO2 catalyst was investigated under the feeding of a raw material gas containing oxygen of 1–10 vol % concentration. The presence of oxygen greatly improved the methanati...

Technologies for the recovery of carbon from greenhouse gases such as carbon dioxide and methane in the solid state will lead to the development of a low-carbon society. For the purpose of realizing such technology, we constructed a catalytic reaction system that continuously captures solid carbon while producing synthesis gas by dry reforming of CH4 (DRM). The constructed reaction system exhibited high DRM activity without catalyst deterioration, with a maximum rate of 20.3% for capturing solid carbon. The use of an iron-based wall-type catalyst and the control of the capturing temperature were effective in improving the carbon capturing rate. We have succeeded in developing a novel catalytic reaction system that can collect solid carbon at a much lower temperature than that by methane decomposition. It was considered that carbon deposition from synthesis gas proceeds via a reaction mechanism which includes formation of cementite (Fe3C). The quality of the collected carbon varied depending on the capturing conditions. In particular, it was confirmed that carbon subjected to higher temperatures contained carbon-nanotubes (CNTs) with high crystallinity and elongation.

β-carotene (BC) is one of the naturally occurring dyes belonging to the carotenoids group. Although it is more environmentally friendly and better suited for humans compared with synthetic dyes, it destabilizes with light and heat, easily losing its color under irradiation. Extended application of BC are therefore limited. The aim of this study is to improve the stability of BC by intercalation into the montmorillonite layers modified with a cationic surfactant, by a simple mixing and minimal solvent use. The physical mixing of small quantities of concentrated BC/hexane solutions with organo-modified montmorillonite successfully resulted in the composite material. The length and the number of alkyl chains of the surfactant used for the organic modification influenced the stability enhancement of the incorporated dye. The improved stability of the dye molecules incorporated in the interlayer space was found to be due to restricted contact with atmospheric oxygen.

The purpose of this study is to develop a powerful CO2 methanation process using a variety of structured Ni/CeO2 catalysts. Various configurations of metallic honeycomb-type catalysts, which are plain, stacked, segment, and multi-stacked were constructed and tested under various reaction conditions; i.e. inlet temperature, feed flow rate and CO2 partial pressure. Effects of the developed configurations including stack and gap distance were examined. The random-flow channels of stacked type and the gap distance of segment type could improve the catalytic activity, resulting in high CO2 conversion. Under industrial-like high feed rate condition and pure feed gas component, a moderate hot spot over the multi-stacked catalyst was observed and reported for the first time. The moderate hot spot reboosted the conversion to a high level even at high feed flow rate condition of 3000 mL/min (contact time of 235 ms). As a result, high CO2 conversion > 90%, high CH4 selectivity > 99.5%, and high stability with dropped conversion p C O 2 / p H 2 = 0.12 / 0.88 . The stability of the Ni/CeO2 catalyst under the moderate hot spot condition was revealed by BET, SEM and XRD analyses.

In our previous study, an iron-supported silica (Fe/SiO2) catalyst exhibiting excellent activity toward propane dehydrogenation with hydrogen sulfide (H2S) co-feeding was identified. This study investigated the potential application of the Fe/SiO2 catalyst for the dehydrogenation of relatively larger molecules, such as iso-pentane (iso-C5), n-pentane (n-C5), and n-butane (n-C4). The reactivity evaluation showed that Fe/SiO2 exhibited a high activity toward iso-C5 dehydrogenation with H2S co-feeding, producing iso-amylenes, such as 2-methyl-1-butene, 2-methyl-2-butene, and isoprene. The total C5-olefin yield obtained using the Fe/SiO2 catalyst was higher than that obtained using Co/SiO2 and Ni/SiO2 catalysts. When Fe/SiO2 was applied to the dehydrogenation of n-C4 and n-C5 with H2S co-feeding, C4- and C5-olefins were obtained, respectively, with relatively high selectivities. In particular, the Fe/SiO2-catalyzed n-C4 dehydrogenation exhibited greater selectivity than iso-C5 and n-C5 dehydrogenations; the product of the n-C4 dehydrogenation was stable for 20 h.

We prepared Ni–Ce/Al-MCM-41 catalyst with enhanced activity at low temperatures via one-pot hydrothermal synthesis using kaolin as a silica precursor for CO2 methanation and investigated the influence of Ce addition on the catalytic activity enhancement. The as-synthesized Al-MCM-41 possessed hexagonal mesoporous silica with a surface area of 436 m2/g and a mesopore of 3.8 nm, allowing the incorporation of Ni and Ce into the Al-MCM-41 structure. In a fixed-bed tubular reactor, the catalytic performance of the as-prepared catalyst was evaluated in terms of CO2 conversion, CH4/CO selectivity, CH4 yield, reaction rates per catalyst mass (rm), and catalyst surface (rs), TOF, activation energy, and the deactivation rates of its corresponding activities at 250–550 °C and 1 atm. As the Ce content increased, the catalytic activity greatly improved due to the improved Ni dispersion and higher CO2 adsorption, although the porosity of the catalyst significantly decreased. With the optimum Ce content, 100% CH4 yield was achieved at 350 °C and weight hourly space velocity (WHSV) = 20,000 mL g−1 h−1. The optimum catalyst also exhibited high stability with a deactivation rate of −0.072% YCH4 g−1 h−1 over 76 h, attributed to the strong interaction between Ce and Al in Al-MCM-41.

The dry reforming of methane (DRM) is an important reaction process for producing useful synthesis gas from greenhouse gases such as CO2 and CH4. The objective of this study was to develop a combined system that continuously produced of synthesis gas (via dry reforming) and captured post-reformer carbon solids (via carbon capture). The relationship between the DRM reaction condition and the carbon deposition phenomena at the capture stage was investigated. The Ni/Al2O3 structured catalyst showed high DRM activity and stability under the conditions of CO2/CH4 ≥ 1.2 at 700 °C, whereas the most effective conditions for carbon capture occurred at 520–650 °C when the ratio of CO2/CH4 = 1.0. The carbon morphology (e.g., carbon nanotubes and nanofibers) also changed as a function of the capturing temperature. This constructed system would be a novel technology for the effective utilization of CO2 and CH4.

In this study, we demonstrate for the first time, a novel and facile one-pot microwave-assisted synthesis of prGO at shorter time period and lower temperature employing hydrochloric acid as an etching agent. Modified porous reduced graphene oxide (prGO) not only avoids the restacking of prGO layers, but also the existence of pores promotes improvement of material transport efficiency. Herein, physical and chemical characterization confirms the presence of macro/mesopores in the obtained prGO without any restacking issue, unlike reported rGO studies. The synergistic effect of the interconnected macro/mesopores provides facile ion transport pathways with the favorable electrolyte contact when compared to the reported rGO studies. In addition, the presence of macropores can shorten the transfer path distance of electrons/ions to the electroactive sites thereby enhancing specific capacitance. As a result, the synthesized prGO shows excellent specific capacitance of 568.5 F g−1 at 1 A g−1 with a remarkable capacity retention after longer charge/discharge cycles. The proposed synthesis approach can be employed to develop prGO based electrode material for various supercapacitor devices.

The aim of this study is to develop a noble-structured catalyst for methane decomposition to produce pure hydrogen. The Ni/Al2O3 structured catalyst, which was prepared by electroless plating with NaBH4 as the reducing agent, showed a higher activity and stability, indicating the advantage for ensuring the flow path. After a steam treatment to remove the deposited carbon, the decomposition performance of the structured catalyst was regenerated.

The purpose of this study is to construct a honeycomb-type structured catalyst with a high methanation performance to effectively transform CO2 to CH4. To select the best methanation component for structuring, a 10 wt% Ni-loaded granular catalyst was prepared by evaporation to dryness using Al2O3, TiO2, ZrO2, Y2O3, MgO and CeO2 as the support materials. The granular Ni/CeO2 catalyst displayed the highest activity at 200–500 °C, while the granular Ni/Al2O3, Ni/MgO and Ni/TiO2 catalysts showed low CO2 conversions. The variable affecting the Ni/CeO2 catalyst having a high performance would be related to the large amount of adsorbed CO2 and the production of many chemical species that originated from the CO2 on the surface. The structured catalyst with the Ni/CeO2 component was prepared by a wash-coating method on an aluminum substrate with a honeycomb-fin configuration. The prepared catalyst showed a high methanation performance, indicating that the cell density and the configuration of the honeycomb-fin clearly influenced the performance. Especially, the structured catalyst with the stacked-type-fin enhanced the methanation performance that improved the mass transfer properties in the reaction field. Furthermore, the structured Ni/CeO2 catalyst showed a steady catalytic performance that maintained the high activity and the high selectivity during a durability test at 350 °C. The honeycomb-type catalyst developed in this study has the potential to be a practicable catalyst for producing energy resources from CO2.

This study deals with the development of a high performance catalyst for the water gas shift reaction (WGS) by doping a promoter (Cr, Mn, Co, Ni, Cu) and optimizing the potassium loading on a structured-type iron oxide catalyst. Doping a promoter was effective for enhancing the WGS activity over the iron oxide-type catalyst, except for the Mn- and Cu-doping. Especially, the Ni-doping catalyst displayed a better performance than the other catalysts. In addition, loading a potassium component was found to have a positive effect on suppression of methanation as well as a drastic enhancement of the WGS activity.

The aim of this study was to clarify the effect of the non-stoichiometry in the A x CrO3−δ (A: La, Pr, Nd, 0.90 ≤ x ≤ 1.05) perovskite-type oxide on the dehydrogenation performance of propane using steam (DHP-S). The slight change in the molar ratio of the A-site (=La, Pr, Nd) to the B-site cation (=Cr) from the stoichiometric composition (A/B = 1) significantly affected the dehydrogenation performance. For the La-based catalyst, the La x CrO3−δ catalyst with 0.90 ≤ x ≤ 0.97 displayed a relatively high activity, while the catalyst with 0.97

This study analyzed the icosahedral Pt55 cluster on the surface of La2O3 by density functional theory (DFT) calculations. The oxygen adsorption energy (ΔE) for the supported Pt55 cluster was different from the ΔE value for the Pt55 cluster without oxide supports. Moreover, the ΔE values for the supported Pt55 cluster depend on adsorption sites. This study applied the idea of Electronic Metal-Support Interaction (EMSI), and proposed the concept of “effective chemical potential (μeff)”. According to DFT calculation, the μeff values of supported Pt55 cluster were the intermediate values between the chemical potential values of Pt55 without oxide support (μPt55) and La2O3 (μLa2O3) (i.e. μPt55

Assuming the treatment of exhaust gas from an industrial process, the methanation characteristics of a Ru/CeO2 catalyst are investigated when oxygen coexisted in the raw material gas. The change in oxygen concentration significantly affected methanation activity, and above 2 vol%, the methanation started autonomously at a room-temperature region, demonstrating auto-methanation (AM) behavior. In this case, oxygen selectively combused hydrogen and did not burn the produced methane. The start-up state and heat generation state of the AM in the room-temperature region are summarized in the mapping information using the oxygen concentration in the raw material gas and feeding flow rate as parameters. The AM that started at room temperature demonstrated constant activity and methane selectivity for a considerably long time, as well as constant methanation characteristics even during daily start-up and shut down (DSS) operations, which repeatedly starts and shuts down. The change in the surface morphology of the Ru/CeO2 catalyst in the DSS operation is insignificant. Thus, the methanation system constructed in this study is considered to be highly applicable as an industrial CO2 treatment technology.

This study estimated the oxygen adsorption energy (ΔEO ads.) for the supported precious metal (PM) clusters (Pt3, Pd3, Rh3 or Au3) on support oxides (TiO2, ZrO2, Al2O3, La2O3, BaO or K2O). The estimated ΔEO ads. values depend on the PM types as well as the types of support oxides. This study tried to predict the ΔEO ads. values by simple calculations. The d–band center theory could describe the ΔEO ads. values for the PM3 cluster under a vacuum condition (PM3 cluster without support oxides), namely, the interactions between the PM3 clusters and O atom depended on the d-band center (ed) values of the PM3 clusters. There was a difference between the ΔEO ads. values for the supported PM3 clusters and the PM3 clusters under the vacuum condition. This study succeeded in describing the difference by the HSAB (Hard-Soft-Acid-Base) concept. Finally, this study proposed a simple equation to predict the ΔEO ads. values for the supported PM clusters. The proposed equation was derived from physicochemical considerations of the d–band center theory and HSAB concept, moreover, the equation contains only one free (adjustable) parameter.

The CO2 methanation for transition-metal catalysts loaded on various oxide-supports was investigated under feeding with a raw material gas containing oxygen. The co-feeding of the oxygen greatly improved methanation performance for Ni- and Ru-based catalysts, because of the high thermal energy generated from hydrogen–oxygen combustion. Especially, Ni/CeO2, Ni/ZrO2, Ni/Y2O3, and Ni/Al2O3 catalysts and the prepared ruthenium catalysts demonstrated high activity and high methane-selectivity even in a region at room temperature and atmospheric pressure. The auto-methanation (AM) phenomenon, which is reported in the world for the first time, proceeded over these catalysts. Compared to that of the Ni-based catalyst, the AM activity of the Ru-based catalyst was approximately 10% higher. Although it was generally predicted that the produced methane was combusted by the co-fed oxygen, yet such methane combustion was not observed so as that the minimum ignition energy of methane–oxygen is much larger than that of hydrogen–oxygen.