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The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability. [ABSTRACT FROM AUTHOR]

The effect of the crystalline phase of alumina on ammonia decomposition over alumina-supported ruthenium (Ru) catalysts was examined. Various Ru catalysts supported on different alumina (α-Al 2 O 3 , κ-Al 2 O 3 , θ-Al 2 O 3 , δ-Al 2 O 3 , η-Al 2 O 3 , and γ-Al 2 O 3) were prepared using a wet impregnation method. The prepared catalysts were characterized using inductively coupled plasma-optical emission spectroscopy, N 2 physisorption, X-ray diffraction, transmission electron microscopy, and CO chemisorption. The Ru dispersion for Ru/Al 2 O 3 was reduced without a calcination step in the following order: Ru/α-Al 2 O 3 < Ru/κ-Al 2 O 3 < Ru/θ-Al 2 O 3 < Ru/δ-Al 2 O 3 < Ru/η-Al 2 O 3 < Ru/γ-Al 2 O 3. Among them, Ru/α-Al 2 O 3 showed the highest catalytic activity for ammonia decomposition. Moreover, the effect of calcination temperature before the reduction step was investigated. Ru particle size and morphology were confirmed to change through the calcination process. Ru/κ-Al 2 O 3 with Ru particle sizes ranging between 7 and 8 nm exhibited the highest ammonia decomposition rate among Ru/Al 2 O 3 catalysts calcined at different temperatures and reduced at 573 K. Therefore, Ru dispersion and its morphology, which can be controlled by the support and calcination temperature, are critical factors for hydrogen production through ammonia decomposition over Ru/Al 2 O 3 catalysts. [Display omitted] • NH 3 decomposition was performed over Ru/Al 2 O 3 catalysts. • The effect of the crystalline phases of alumina was evaluated. • The effect of the Ru dispersion and morphology was investigated. • All data support that NH 3 decomposition is a structure sensitive reaction. • The relationship between the catalytic activity and Ru dispersion is discussed. [ABSTRACT FROM AUTHOR]

Abstract: We prepared Ru catalysts supported on various aluminum oxides with different crystalline phases, viz. α-Al2O3, κ-Al2O3, γ-Al2O3, η-Al2O3, δ-Al2O3 and θ-Al2O3, by the incipient wetness method and applied them to the selective CO oxidation in a hydrogen-rich stream. For comparison, the complete CO oxidation in the absence of H2 was also carried out over the same catalysts. Ru/α-Al2O3 showed the highest CO conversion among the tested catalysts, especially at low temperatures, irrespective of the presence of H2. For all of the catalysts, the catalytic activity for CO oxidation was much suppressed in the absence of H2 compared with that in the presence of H2. Several techniques: N2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), CO chemisorption, temperature-programmed oxidation (TPO), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of CO2 with mass spectroscopy and transmission electron microscopy (TEM) were employed to characterize the catalysts. The least amount of chemisorbed CO and CO2 was obtained at room temperature over Ru/α-Al2O3. The least amount of O2 was chemisorbed during TPO and the oxidized Ru species could be fully reduced in the presence of hydrogen at the lowest temperature over Ru/α-Al2O3 among the Ru/Al2O3 catalysts. Ru/α-Al2O3 can reduce a high inlet concentration of CO to less than 10ppm even in the presence of H2O and CO2 over a wide temperature range. [Copyright &y& Elsevier]

Abstract: We conducted a comparative study for the water-gas shift (WGS) reaction over ceria-promoted Pt catalysts supported on various supports such as γ-Al2O3, SiO2, TiO2 (P-25), CeO2, SiO2-Al2O3, yttria-stabilized zirconia (YSZ) and ZrO2 in a rather severe reaction condition such as 6.7vol.% CO, 6.7vol.% CO2, and 33.2vol.% H2O in H2. Among them, Pt-Ce/TiO2 showed the highest WGS activity especially at low temperatures. The effect of preparation sequences on the catalytic activity was also examined for ceria-promoted Pt supported on TiO2 and Pt-Ce/TiO2 prepared with a single-step co-impregnation method showed the highest water-gas shift activity. The CO chemisorptions, the temperature-programmed reduction (TPR), an inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and a transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX) were conducted to characterize catalysts. The close correlation between the low-temperature water-gas shift activity and the amounts of chemisorbed CO as well as the degree of interaction between Pt and ceria has been observed. This Pt-Ce/TiO2 showed the more stable catalytic activity in the cyclic operation and the start-up/shut-down operation compared with the conventional Pt-Ce/CeO2. [Copyright &y& Elsevier]

Abstract: We prepared various Ru catalysts supported on silicas with different surface areas by an incipient wetness impregnation method and applied them in selective CO oxidation in a H2-rich stream. For comparison, complete CO oxidation was also examined. The physical properties were probed with N2 physisorption. The Ru dispersion was measured with CO chemisorption and transmission electron microscopy (TEM). The interaction between the catalyst surface and a reactant was examined with O2 chemisorption, temperature-programmed oxidation (TPO), and temperature-programmed reduction (TPR). The BET surface area and total pore volume of the silica decreased with increasing calcination temperature. The average pore diameter of the silica increased with calcination temperature. The existence of micropores was not observed in the silica calcined in air at temperatures of 1103K and above. The amount of CO and O2 chemisorbed on Ru/SiO2 at 300K decreased with decreasing surface area of the silica. The particle size of Ru metal in Ru/SiO2 generally increased with decreasing surface area of the silica. Ru/SiO2 with a larger Ru particle size showed superior catalytic activities for the complete CO oxidation and the selective CO oxidation in a H2-rich stream, compared to Ru/SiO2 with a smaller Ru particle size, which might be due to the resistance to oxidation of Ru metal into RuO x species. The Ru particle size also affects the fraction of active surface oxygen. Selected Ru/SiO2 catalysts can reduce a high inlet CO concentration to less than 10ppm even in the presence of H2O and CO2. [Copyright &y& Elsevier]

• Core–shell Al@Al2O3 was used as the support in supported Ni catalysts. • The Al@Al2O3 is better than γ-Al2O3 to develop a highly efficient Ni-based catalyst. • The deposition–precipitation method outperforms the wet impregnation method. • Higher Ni dispersion resulted in better catalytic performance for CO methanation. • The higher density of medium basic sites increases the CO 2 methanation activity. Core–shell Al@Al 2 O 3 , which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO 2 methanation. The core–shell micro-structured support (Al@Al 2 O 3) helped develop a highly efficient Ni-based catalyst compared with conventional γ-Al 2 O 3 for these reactions. Moreover, the deposition–precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N 2 physisorption, H 2 chemisorption, CO 2 chemisorption, temperature-programmed reduction with H 2 , temperature-programmed desorption after CO 2 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al 2 O 3 as the support and the deposition–precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO 2 adsorption capacity observed for Ni/Al@Al 2 O 3 helped increase catalytic activity for CO 2 methanation. [ABSTRACT FROM AUTHOR]

• Core-shell Al@γ-Al 2 O 3 was applied to the preferential CO oxidation in H 2 (PROX). • Ru/Al@γ-Al 2 O 3 shows the better PROX performance than Ru/α-Al 2 O 3 and Ru/γ-Al 2 O 3. • The effect of surface oxidation of Ru metal on PROX activity is important. • The surface oxidation of Ru metal on Al@γ-Al 2 O 3 was suppressed. • Ethanol-TPD reveals that Al@γ-Al 2 O 3 has different surface property with γ-Al 2 O 3. The Al@γ-Al 2 O 3 core-shell microstructures prepared from aluminum particles by hydrothermal surface oxidation were superior to the conventional alumina support owing to the facile heat flux through the metal-ceramic composite structures. The Ru catalysts supported on Al@γ-Al 2 O 3 were used for the preferential CO oxidation (PROX) reaction, which is a highly exothermic reaction requiring high heat flux. For comparison, commercially available α-Al 2 O 3 and γ-Al 2 O 3 were also used as catalyst supports. The catalysts were characterized by N 2 -physisorption, X-ray diffraction, CO chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ethanol (ethanol-TPD) and ammonia (NH 3 -TPD), and temperature-programmed oxidation (TPO). The Ru/α-Al 2 O 3 catalyst with the lowest Ru dispersion showed the best PROX performance among the tested catalysts in the absence of CO 2 and H 2 O. Even though Ru/Al@γ-Al 2 O 3 and Ru/γ-Al 2 O 3 had similar Ru dispersions, the former catalyst exhibited a much better PROX performance than the latter. This could be explained by the fact that the Ru metal deposited on Al@γ-Al 2 O 3 was more resistant to surface oxidation as compared to that on γ-Al 2 O 3 , based on the TPO results. A lower desorption temperature of ethanol was observed over Al@γ-Al 2 O 3 than over γ-Al 2 O 3 during ethanol-TPD experiments, even though both supports had similar amounts of acid sites, as determined by NH 3 -TPD. Among the tested catalysts, Ru/Al@γ-Al 2 O 3 also showed the best PROX performance in the presence of CO 2 and H 2 O. A further enhancement in the PROX performance was achieved by increasing the Ru metal particle size from 1.4 to 2.6 nm by pretreating the Ru/Al@γ-Al 2 O 3 catalyst with 1 mol% O 2 in He at 150 ℃. [ABSTRACT FROM AUTHOR]

We report the barium zirconate supported NiO x catalysts (NiO x /BZO) for dry reforming of methane and feasibility test for their industrial application by using temperature-regulated chemical vapor deposition together with extrusion. Nickel oxide nanoparticles are well deposited and dispersed on BZO powders as well as structures in a gear form, showing high catalytic activity and extraordinary stability even at relatively lower temperature and higher space velocity. The NiO x /BZO catalyst are highly coke resistant for 50 h operation with almost negligible agglomeration of NiO x nanoparticles. Judging from XPS and high ion conducting properties of BZO supports, the –OH or –O species are expected to play an important role in promoting the self-decoking of surface carbon species to form CO and CO 2. [ABSTRACT FROM AUTHOR]

CO and CO 2 methanation was investigated over Ni catalysts supported on different supports such as γ-Al 2 O 3 , SiO 2 , TiO 2 , CeO 2 , and ZrO 2 . Among them, Ni/CeO 2 was determined to be the most active for CO and CO 2 methanation. These catalytic activities increased with increasing surface area of CeO 2 . To increase the specific catalytic activity for CO and CO 2 methanation, various Ni-CeO 2 catalysts with different Ni contents were prepared using co-precipitation method. The optimum Ni content was determined for both reactions. The prepared catalysts were characterized with inductively coupled plasma-atomic emission spectroscopy, N 2 physisorption, temperature-programmed reduction, temperature-programmed desorption, and X-ray diffraction. The high Ni dispersion and strong CO 2 adsorption appeared to be responsible for the high catalytic activity for CO and CO 2 methanation. This Ni-CeO 2 can be applied to the low-temperature CO and CO 2 methanation reactor to achieve high single-pass conversions of CO and CO 2 . [ABSTRACT FROM AUTHOR]

[Display omitted] • A low-cost copper monometallic catalyst was developed for lignin hydrogenolysis. • Lignin hydrogenolysis into aromatic monomers was conducted in supercritical ethanol. • Reaction conditions were systematically optimized to increase the monomer yield. • Maximally 38.5% of monomer yield was obtained at the optimal condition. • Depolymerized alkali lignin mainly consisted of G-lignin-type monomers. The catalytic hydrogenolysis of lignin has been reported as an effective approach for lignin depolymerization owing to its high efficiency for aromatic monomer production. In this study, a series of copper monometallic catalysts over an MIL-101(Cr) support were synthesized and used for the catalytic hydrogenolysis of alkali lignin using supercritical ethanol. First, the optimal copper catalyst for lignin hydrogenolysis was selected. Subsequently, the reaction conditions for catalytic hydrogenolysis were systematically optimized to maximize the total monomer yield. The optimal conditions were determined to be 6 h of reaction time, 20 min of sonication pretreatment, 50% catalyst loading, and 5% lignin loading. Under these conditions, an aromatic monomer yield of 38.5% was obtained; this depolymerized lignin stream, which is mainly composed of G-type monomers, can serve as a promising aromatic feedstock and carbon source for further microbial upgrading and bioconversion to produce various value-added products. [ABSTRACT FROM AUTHOR]

• Liquid-phase partial oxidation of methane with O 2 was achieved in the presence of H 2. • Pd supported on acid-functionalized porous polymer was used for in situ H 2 O 2 generation. • Fe-ZSM-5 was stable and active for methane oxidation with in situ H 2 O 2. • The combination of these two catalysts showed the TOF of 3.8 h−1 at 30 ℃. Aqueous-phase partial oxidation of methane over a combination of heterogeneous Fe-ZSM-5 and Pd catalysts was demonstrated in the presence of O 2 and H 2. Fe-ZSM-5 catalyst active for partial oxidation of methane with H 2 O 2 was prepared by an ion-exchange method. For comparison, homogeneous Fe species (FeSO 4) were also used as a catalyst for partial oxidation of methane. Several supported Pd catalysts for the direct synthesis of hydrogen peroxide from H 2 and O 2 were prepared using activated carbon (AC), AC treated with sulfuric acid (s-AC), as-synthesized hyper-crosslinked porous polymer (HCPP), HCPP with carboxylic group (c−HCPP), and HCPP with carboxylic and sulfonic groups (c-s−HCPP). Among them, the Pd catalyst supported on c-s−HCPP was effective for generating H 2 O 2 in situ , which enabled methane oxidation over Fe-ZSM-5 without any leaching. [ABSTRACT FROM AUTHOR]