One-pot Evaporation-induced Self-assembly Research Articles

One-pot synthesis of ordered mesoporous NiMo-Al2O3 catalysts for dibenzothiophene hydrodesulfurization

Ordered mesoporous NiMo-Al2O3 catalysts with 20.0wt.% MoO3 and various NiO contents were synthesized by a facile one-pot evaporation-induced self-assembly (EISA) method, using P123 as structure-directing agent and anhydrous ethanol as solvent. The hydrophilic Al-, Ni-, and Mo-containing compounds surrounded the P123 micelles to form a hexagonal mesoporous structure. The NiMo-Al2O3 catalysts were characterized by a series of techniques, including N2 adsorption, XRD, XRF, TEM, SEM, FT-IR, TG-DSC (for the as-synthesized NiMo-Al2O3 precursors), and TPR. The catalytic activities were tested in hydrodesulfurization (HDS) of dibenzothiophene (DBT). Results show that calcination at 500°C can fully remove the surfactant and solvent to form amorphous walls. Molybdenum and nickel atoms were incorporated into the channels of the ordered mesoporous alumina and highly dispersed, maintaining the hexagonal symmetry mesostructures. Incorporations of Ni promoted a transformation of molybdate from tetrahedral to octahedral sites and changed the relative intensities of the TPR peaks. Catalytic results reveal that the ordered mesoporous NiMo-Al2O3 catalysts had high activities towards DBT. Biphenyl was the abundant product in HDS reactions, and direct desulfurization was the dominant route. A high HDS activity was observed with a Ni/Mo molar ratio of 1:1, which was attributed to more easily reducible molybdate and better dispersion of the MoS2 nanoparticles. The ordered mesoporous NiMo-Al2O3 catalysts, synthesized by this facile one-pot EISA method, provide a new alternative for industrial HDS process.

CO methanation on ordered mesoporous Ni–Cr–Al catalysts: Effects of the catalyst structure and Cr promoter on the catalytic properties

CO methanation is the main route in industry to produce synthetic natural gas (SNG), and the conventional Ni-based catalysts for this reaction often deactivate severely because of sintering of the Ni particles and coke formation on them. To overcome these technical barriers, we designed and synthesized a group of ternary Ni–Cr–Al metal oxide composites with ordered mesoporous structure and various Cr and Ni contents via a one-pot evaporation-induced self-assembly strategy and tested them for CO methanation to produce SNG. The support and the catalysts before and after the catalytic reaction were thoroughly characterized. It was found that, after reduction at 700°C, metallic Ni particles were generated and anchored in the ordered mesoporous alumina channels while the Cr species started to surround the metallic Ni particles. The long-range ordered mesoporous structure could be maintained well when the total loading of nickel and chromium oxides was below 22wt.%. In general, the optimized ordered mesoporous Ni–Cr–Al catalysts show much better anti-coking and anti-sintering properties and much higher catalytic activity and stability than the conventional Ni catalysts. The improved catalytic performance is attributed to the reduced Ni particle size, the confinement effect of the mesoporous materials, and the promoting effect of Cr, which can significantly reduce the Ni particle size and increase the H2 uptake. These findings shed light on the design of ordered mesoporous alumina-supported materials with high loading of active metal oxides for many high-temperature reactions.

Highly stable mesoporous NiO–Y2O3–Al2O3catalysts for CO2reforming of methane: effect of Ni embedding and Y2O3promotion

A series of mesoporous NiO–Y2O3–Al2O3composite oxides with different yttrium contents were synthesized by either a one-pot evaporation-induced self-assembly (EISA) method or impregnation for carbon dioxide reforming of methane (CRM).

Faculty acceptance testing of multimedia-based e-learning resources on core competencies for interprofessional collaborative practice

Ordered mesoporous Cu–Mg–Al composite oxides were synthesized via the one-pot evaporation-induced self-assembly strategy. Using this method, copper was first homogeneously incorporated into the ordered mesoporous spinel matrix. After H2 reduction treatment, according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, copper existed as metallic nanoparticles with the size of 6–10 nm that well decorated the parent mesoporous skeleton. The metallic nanoparticles were then re-oxidized to copper oxide when exposed to air or during CO oxidation reaction at low temperatures. Thus, copper migrated from bulk spinel phase to the surface after the reduction–oxidation treatment. Moreover, the copper on the surface was re-incorporated into the bulk spinel phase by further thermal treatment at much higher temperature in the presence of air. The correlation between the state of copper in the mesoporous composite oxides and the catalytic performance toward CO oxidation was studied. It was found that copper existed as oxide nanoparticles on the surface of mesoporous Mg–Al skeleton is much more active than that existed as lattice Cu ions in spinel phase.

Effect of reduction–oxidation treatment on structure and catalytic properties of ordered mesoporous Cu–Mg–Al composite oxides

Ordered mesoporous Cu–Mg–Al composite oxides were synthesized via the one-pot evaporation-induced self-assembly strategy. Using this method, copper was first homogeneously incorporated into the ordered mesoporous spinel matrix. After H2 reduction treatment, according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, copper existed as metallic nanoparticles with the size of 6–10nm that well decorated the parent mesoporous skeleton. The metallic nanoparticles were then re-oxidized to copper oxide when exposed to air or during CO oxidation reaction at low temperatures. Thus, copper migrated from bulk spinel phase to the surface after the reduction–oxidation treatment. Moreover, the copper on the surface was re-incorporated into the bulk spinel phase by further thermal treatment at much higher temperature in the presence of air. The correlation between the state of copper in the mesoporous composite oxides and the catalytic performance toward CO oxidation was studied. It was found that copper existed as oxide nanoparticles on the surface of mesoporous Mg–Al skeleton is much more active than that existed as lattice Cu ions in spinel phase.

One-pot synthesis of ordered mesoporous Ni–V–Al catalysts for CO methanation

Preventing both the sintering of Ni particles and the coke formation in supported nickel (Ni) catalysts is a great challenge in catalysis. To address the problem, in this work, we have designed and synthesized a series of ternary Ni–V–Al metal oxide composites with desired structure and composition, for example, the ordered mesoporous structure and various V contents. The catalysts are synthesized via a facile one-pot evaporation-induced self-assembly strategy and are used in CO methanation reaction to produce synthetic natural gas. Our results showed that the Ni–V–Al catalysts with ordered mesopores have better catalytic properties than the impregnation-derived Ni catalysts supported on alumina supports with ordered mesopores or with unordered mesopores. The addition of proper amount of vanadium oxide in the ordered mesoporous Ni–V–Al catalysts further promotes the catalytic activity toward CO methanation. In a 110h atmospheric-pressure lifetime test, the ordered mesoporous Ni–V–Al catalyst showed significant improvement in both anti-coking and anti-sintering, mainly because of the smaller Ni particle size (<5nm), the confinement effect of the mesopore channels as well as the incorporation of the vanadium promoter as compared to the catalyst without ordered mesopores.

Novel straight synthesis of super-microporous Cu/Al2O3 catalyst with high CH4-SCR-NO activity

A super-microporous nanocrystalline 15mol% copper–alumina (pore size 1 to 2nm) was prepared via a facile one-pot evaporation-induced self-assembly (EISA) strategy with an economic template. After removing the template at 500°C, the sample exhibited high specific surface area (larger than 580m2/g), narrow pore size distribution and high thermal stability. Owing to its large surface area and the good dispersion of active Cu centers, the sample exhibited an enhanced catalytic activity in the selective catalytic reduction (SCR) of NO with methane than those of conventional Cu/Al2O3 catalysts. Additionally, it presented remarkable activity in direct NO decomposition.

One-pot synthesis of ordered mesoporous transition metal–zirconium oxophosphate composites with excellent textural and catalytic properties

A series of ordered M–X–ZrPO materials were successfully synthesized via a facile and general one-pot evaporation-induced self-assembly (EISA) strategy.

Methane reforming with carbon dioxide over mesoporous nickel–alumina composite catalyst

A mesoporous nickel–alumina composite catalyst prepared by one-pot evaporation-induced self-assembly (EISA) method, and a nickel supported EISA synthesized alumina catalyst prepared by impregnation method, were comparably studied for carbon dioxide reforming of methane reaction. The catalysts were characterized by N2 physical adsorption, XRD, TPR, TEM, H2 chemisorption and TG techniques. Although both mesoporous catalysts were active and stable for CO2 reforming of CH4, one-pot EISA synthesized catalyst showed superior catalytic performance to that prepared by impregnation method. It could be attributed to the higher nickel dispersion and stronger metal to support interaction of one-pot EISA synthesized catalyst, since small nickel crystalline size could retard coking and strong metal to support interaction could resist sintering.