Leilei Xu

Significant roles of mesostructure and basic modifier for ordered mesoporous Ni/CaO–Al2O3 catalyst towards CO2 reforming of CH4

An ordered mesoporous CaO–Al2O3 composite oxide had been designed and prepared via improved evaporation induced self-assemble strategy (EISA). The resultant material was utilized as the support of Ni based catalyst for CO2 reforming of CH4. In order to study the roles of the ordered mesopore structure and basic modifier in promoting the catalytic properties toward the CO2 reforming of CH4 reaction, non-mesoporous CaO–Al2O3 without ordered mesostructure and ordered mesoporous Al2O3 without basic modifier were also synthesized, respectively. It was found that both the ordered mesostructure and CaO basic modifier showed significant effects in promoting catalytic activity, stability and suppressing the carbon deposition during their 100 h long term stability tests. Compared with traditional supported catalysts, the confinement effect of the mesoporous catalysts could effectively inhibit the thermal sintering of the Ni particles. Furthermore, the sorts of coke species over the spent catalysts and the mechanism of catalyst deactivation were also carefully investigated. Therefore, the present ordered mesoporous CaO–Al2O3 composite oxide will be a potential carrier for Ni-based catalysts for CO2 reforming of CH4 and even other reactions.

One-step synthesis of ordered mesoporous CoAl2O4 spinel-based metal oxides for CO2 reforming of CH4

A series of ordered mesoporous CoAl2O4 spinel-based metal oxides with different Co content were facilely synthesized via a one-step evaporation-induced self-assembly method and utilized as catalysts for CO2 reforming of CH4. These mesoporous catalysts, which have unique textural properties and outstanding thermal stabilities, exhibited excellent catalytic performances under various reaction conditions. The ordered mesostructures in the catalysts could provide sufficiently accessible Co active sites for gaseous reactants and stabilize Co metallic nanoparticles via confinement effects within the mesoporous frameworks. These mesoporous catalysts exhibited better anti-coke abilities than non-mesoporous catalysts or traditional supported catalysts, thus acting as a promising series of potential catalyst candidates for CO2 reforming of CH4.

CO2 methanation over a Ni based ordered mesoporous catalyst for the production of synthetic natural gas

Ni based catalysts have been considered as ideal candidates for the CO2 methanation reaction to generate synthetic natural gas owing to its high activity and low cost. In the present manuscript, we described a kind of ordered mesoporous NiO–Al2O3 composite metal oxide, fabricated by a one-step evaporation induced self-assembly (EISA) strategy, which was utilized as the catalyst for CO2 methanation. The obtained material was characterized by XRD, N2 adsorption–desorption, TEM-EDS, H2-TPR, and XPS techniques. The mesoporous catalyst with a large specific surface area (232.8 m2 g−1), big pore volume (0.43 cm3 g−1), tunable pore diameter (9.5 nm), strong metal–mesoporous framework interaction, and outstanding thermal stability (up to 800 °C) had a better catalytic performance than traditional non-mesoporous and supported reference catalysts. The ordered interconnected mesoporous network was beneficial to the mass diffusion of the gaseous reactants and enhanced the catalytic performance by providing sufficient accessible metallic active centers for the gaseous reactants. Besides, the Ni metallic nanoparticles could be stabilized via the space confinement effect of the mesoporous framework, finally reinforcing the catalytic stability. Generally, the presently reported ordered mesoporous NiO–Al2O3 composite oxide promises to be a potential catalyst candidate for CO2 methanation.

Carbon Dioxide Reforming of Methane over Cobalt‐Nickel Bimetal‐Doped Ordered Mesoporous Alumina Catalysts with Advanced Catalytic Performances

Co‐Ni bimetal‐doped ordered mesoporous Al2O3 composite oxides with different Co/(Co+Ni) ratios were designed and fabricated by a one‐pot evaporation‐induced self‐assembly method. The obtained materials, which had an ordered mesostructure and outstanding thermal stability, were investigated as catalysts for the CO2 reforming of CH4. The effects of the Co/(Co+Ni) molar ratios and ordered mesostructure on the catalytic performances were investigated systematically. The ordered mesoporous Co‐Ni bimetallic catalysts exhibited both higher catalytic activities and better anticoke properties than the corresponding monometallic materials because of the Co‐Ni synergistic effect. Furthermore, the ordered mesostructure could promote the catalytic performances significantly by providing gaseous reactants with enough accessible metallic active centers and stabilizing the metallic nanoparticles through the confinement effect of the mesoporous framework. As a result, these mesoporous Co‐Ni bimetallic catalysts had more enhanced catalytic properties and anticoke ability than traditional supported catalysts toward the CO2 reforming of CH4, which promises a series of potential catalyst candidates.

Alkaline-promoted Ni based ordered mesoporous catalysts with enhanced low-temperature catalytic activity toward CO2 methanation

For CO2 methanation reaction, a Mg species is often utilized as the alkaline promotor for Ni based catalysts to enhance the low-temperature catalytic activity. Herein, based on a pioneer ordered mesoporous NiO–Al2O3 catalyst, a Mg alkaline promotor had been incorporated into the ordered mesoporous framework via a one-pot evaporation induced self-assembly (EISA) strategy. As a result, the ordered mesoporous NiO–MgO–Al2O3 composite oxides with Mg/Al molar ratios in a wide range (0–10%) were successfully fabricated and directly utilized as the catalysts for CO2 methanation reaction. These mesoporous catalysts were carefully characterized by X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy, selected area electron diffraction, energy dispersive spectrometer, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and CO2 temperature-programmed desorption measurements. It was found that the ordered mesoporous materials with large specific surface areas (180.8–232.8 m2 g−1), big pore volumes (0.37–0.43 cm3 g−1), and narrow pore size distributions (around 9.5 nm) could be successfully retained after the calcination at 700 °C. The highly dispersed Ni species were strongly interacted with the mesoporous framework in the form of NiAl2O4 spinel. The incorporation of the Mg progressively increased the surface basicity of these catalysts, which could intensify the chemisorption and activation of CO2 during the CO2 methanation reaction. Therefore, the low-temperature catalytic activity was significantly enhanced. The “volcano-shape curve” relationship between the Mg/Al molar ratio and catalytic activity had been interestingly observed, suggesting only appropriate surface basicity could obtain the optimum catalytic activity. Besides, there was no evident deactivation over these mesoporous catalysts after 50 h long-term stability tests due to the confinement effect of the mesoporous framework. Therefore, the present ordered mesoporous NiO–MgO–Al2O3 materials could be considered as a series of potential catalyst candidates for CO2 methanation.

Thermally stable Ir/Ce0.9La0.1O2 catalyst for high temperature methane dry reforming reaction

In this study, the use of a thermally stable Ir/Ce0.9La0.1O2 catalyst was investigated for the dry reforming of methane. The doping of La2O3 into the CeO2 lattice enhanced the chemical and physical properties of the Ir/Ce0.9La0.1O2 catalyst, such as redox properties, Ir dispersion, oxygen storage capacity, and thermal stability, with respect to the Ir/CeO2 catalyst. Hence, the Ir/Ce0.9La0.1O2 catalyst exhibits higher activity and stabler performance for the dry reforming of methane than the Ir/CeO2 catalyst. This observation can be mainly attributed to the stronger interaction between the metal and support in the Ir/Ce0.9La0.1O2 catalyst stabilizing the catalyst structure and improving the oxygen storage capacity, leading to negligible aggregation of Ir nanoparticles and the Ce0.9La0.1O2 support at high temperatures, as well as the rapid removal of carbon deposits at the boundaries between the Ir metal and the Ce0.9La0.1O2 support.