Well-ordered Cs–Ru/@SBA-15 nanocomposite materials for low pressure ammonia synthesis

2020 ◽  
Vol 4 (11) ◽  
pp. 5802-5811
Author(s):  
Shih-Yuan Chen ◽  
Masayasu Nishi ◽  
Albert Chang ◽  
Wei-Chih Hsiao ◽  
Takehisa Mochizuki ◽  
...  
Keyword(s):  
Active Sites ◽  
Ammonia Synthesis ◽  
Low Pressure ◽  
Nanocomposite Materials ◽  
Inert Support

An active and durable Ru-based catalyst using an inert support such as SBA-15 for low pressure ammonia synthesis can be prepared, where the Cs-promoted Ru active sites are delicately built in the nanospace.

scholarly journals Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia synthesis

2021 ◽  
Author(s):  
Jinsun Lee ◽  
Xinghui Liu ◽  
Ashwani Kumar ◽  
Yosep Hwang ◽  
Eunji Lee ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Active Sites ◽  
Rational Design ◽  
Ammonia Synthesis ◽  
Reduction Reaction ◽  
Band Structures ◽  
Electronic Band ◽  
Defect Sites ◽  
Electronic Band Structures ◽  
Reaction Routes

This work highlights the importance of a rational design for more energetically suitable nitrogen reduction reaction routes and mechanisms by regulating the electronic band structures with phase-selective defect sites.

scholarly journals Energy Efficient and Intermittently Variable Ammonia Synthesis over Mesoporous Carbon-Supported Cs-Ru Nanocatalysts

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 406 ◽  
Author(s):  
Masayasu Nishi ◽  
Shih-Yuan Chen ◽  
Hideyuki Takagi
Keyword(s):  
Activated Carbon ◽  
Mesoporous Carbon ◽  
Active Sites ◽  
Carbon Materials ◽  
Ammonia Synthesis ◽  
Molar Ratios ◽  
Free Hydrogen ◽  
Catalytically Active ◽  
Ru Species ◽  
Mesoporous Carbon Materials

The Cs-promoted Ru nanocatalysts supported on mesoporous carbon materials (denoted as Cs-Ru/MPC) and microporous activated carbon materials (denoted as Cs-Ru/AC) were prepared for the sustainable synthesis of ammonia under mild reaction conditions (<500 °C, 1 MPa). Both Ru and Cs species were homogeneously impregnated into the mesostructures of three commercial available mesoporous carbon materials annealed at 1500, 1800 and 2100 °C (termed MPC-15, MPC-18 and MPC-21, respectively), resulting in a series of Cs-Ru/MPC catalysts with Ru loadings of 2.5–10 wt % and a fixed Cs loading of 33 wt %, corresponding to Cs/Ru molar ratios of 2.5–10. However, the Ru and Cs species are larger than the pore mouths of microporous activated carbon (shortly termed AC) and, as a consequence, were mostly aggregated on the outer surface of the Cs-Ru/AC catalysts. The Cs-Ru/MPC catalysts are superior to the Cs-Ru/AC catalyst in catalysing mild ammonia synthesis, especially for the 2.5Cs-10Ru/MPC-18 catalyst with a Ru loading of 10 wt % and a Cs/Ru ratio of 2.5, which exhibited the highest activity across a wide SV range. It also showed an excellent response and stability during cycling tests over a severe temperature jump in a short time, presumably due to the open mesoporous carbon framework and suitable surface concentrations of CsOH and metallic Ru species at the catalytically active sites. This 2.5Cs-10Ru/MPC-18 catalyst with high activity, fast responsibility and good stability has potential application in intermittently variable ammonia synthesis using CO2-free hydrogen derived from electrolysis of water using renewable energy with fast variability.

scholarly journals Essential role of hydride ion in ruthenium-based ammonia synthesis catalysts

2016 ◽  
Vol 7 (7) ◽  
pp. 4036-4043 ◽  
Author(s):  
Masaaki Kitano ◽  
Yasunori Inoue ◽  
Hiroki Ishikawa ◽  
Kyosuke Yamagata ◽  
Takuya Nakao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Essential Role ◽  
Ammonia Synthesis ◽  
Metal Hydrides ◽  
Low Pressure ◽  
Hydride Ion ◽  
Synthesis Catalysts

Ruthenium-loaded metal hydrides with hydrogen vacancies function as efficient catalysts for ammonia synthesis under low temperature and low pressure conditions.

scholarly journals Mild Ammonia Synthesis over Ba-Promoted Ru/MPC Catalysts: Effects of the Ba/Ru Ratio and the Mesoporous Structure

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 480 ◽  
Author(s):  
Masayasu Nishi ◽  
Shih-Yuan Chen ◽  
Hideyuki Takagi
Keyword(s):  
Synergistic Effect ◽  
Mesoporous Carbon ◽  
Active Sites ◽  
Molecular Diffusion ◽  
Ammonia Synthesis ◽  
Mesoporous Structure ◽  
X Ray Diffraction ◽  
Carbon Framework ◽  
Catalytically Active ◽  
Ru Species

A series of novel mesoporous carbon-supported, Ba-promoted, Ru catalysts with Ba/Ru ratios of 0.1–1.6 and a Ru loading of 10 wt% (denoted as 0.1–1.6Ba-10Ru/MPC) were prepared via stepwise impregnation of Ru and Ba precursors on the mesoporous carbon materials. The catalysts were applied to mild ammonia synthesis and compared to reference materials, including an analog of the prepared catalyst with a Ba/Ru ratio of 1.6 and a Ru loading of 10 wt% (denoted as 1.6Ba-10Ru/AC). Characterization by X-ray diffraction (XRD), nitrogen physisorption, and electronic microscopy revealed that the 0.1–1.6Ba-10Ru/MPC catalysts contained Ru particles (approximately 2 nm) that were well-dispersed on the mesoporous structure and nanostructured Ba(NO3)2 species. These species decomposed into amorphous BaOx species, acting as a promoter on the metallic Ru particles forming catalytically active sites for ammonia synthesis. All the 0.1–1.6Ba-10Ru/MPC catalysts showed a synergistic effect of the active Ba and Ru species, which were stabilized in the mesoporous carbon framework with fast molecular diffusion and could effectively catalyze mild ammonia synthesis (280–450 °C and 0.99 MPa) even under intermittently variable conditions, particularly for those with Ba/Ru ratios of >0.5. In contrast, the 1.6Ba-10Ru/AC analog showed poor activity and stability for ammonia synthesis due to the sintering of Ba and Ru particles on the outer surface of the microporous carbon framework, resulting in low molecular diffusion and weak synergistic effect of the catalytically active sites.

scholarly journals Higher Activity of Ni/γ-Al2O3 over Fe/γ-Al2O3 and Ru/γ-Al2O3 for Catalytic Ammonia Synthesis in Nonthermal Atmospheric-Pressure Plasma of N2 and H2

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 590
Author(s):  
Masakazu Iwamoto ◽  
Masataka Horikoshi ◽  
Ryu Hashimoto ◽  
Kaori Shimano ◽  
Tomiko Sawaguchi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Atmospheric Pressure ◽  
Active Sites ◽  
Ammonia Synthesis ◽  
Atmospheric Pressure Plasma ◽  
Nonthermal Plasma ◽  
Synthesis Process ◽  
Efficient Catalyst ◽  
Plasma Reaction ◽  
Activity Sequence

Developing a novel ammonia synthesis process from N2 and H2 is of interest to the catalysis and hydrogen research communities. γ-Alumina-supported nickel was determined capable of serving as an efficient catalyst for ammonia synthesis using nonthermal plasma under atmospheric pressure without heating. The catalytic activity was almost unrelated to the crystal structure and the surface area of the alumina carrier. The activity of Ni/Al2O3 was quantitatively compared with that of Fe/Al2O3 and Ru/Al2O3, which contained active metals for the conventional Haber–Bosch process. The activity sequence was Ni/Al2O3 > Al2O3 > Fe/Al2O3 > no additive > Ru/Al2O3, surprisingly indicating that the loading of Fe and Ru decreased the activity of Al2O3. The catalytic activity of Ni/Al2O3 was dependent on the amount of loaded Ni, the calcination temperature, and the reaction time. XRD, visual, and XPS observations of the catalysts before the plasma reaction indicated the generation of NiO and NiAl2O4 on Al2O3, the latter of which was generated upon high-temperature calcination. The NiO species was readily reduced to Ni metal in the plasma reaction, whereas the NiAl2O4 species was difficult to reduce. The catalytic behavior could be attributed to the production of fine Ni metal particles that served as active sites. The PN2/PH2 ratio dependence and rate constants of formation and decomposition of ammonia were finally determined for 5.0 wt% Ni/Al2O3 calcined at 773 K. The ammonia yield was 6.3% at an applied voltage of 6.0 kV, a residence time of reactant gases of 0.12 min, and PH2/PN2 = 1.

On the mechanism of electrochemical ammonia synthesis on the Ru catalyst

2016 ◽  
Vol 18 (13) ◽  
pp. 9161-9166 ◽  
Author(s):  
Seoin Back ◽  
Yousung Jung
Keyword(s):  
Active Sites ◽  
Hydrogen Adsorption ◽  
Ammonia Synthesis ◽  
Reduction Reaction ◽  
Nitrogen Reduction ◽  
Associative Mechanism ◽  
Ru Catalyst

The nitrogen reduction reaction (NRR) pathways involving various N–N dissociation steps are found to be comparable to the conventional associative mechanism. The competitive hydrogen adsorption and evolution is revealed to negatively affect the NRR for two reasons, an increase in NRR overpotentials as a function of partial H-coverages as well as a decreased number of active sites.

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