Effect of La2O3 on Ru/CeO2-La2O3 Catalyst for Ammonia Synthesis

Boosting the Catalytic Performance of Co/Mg/La Catalyst for Ammonia Synthesis by Selecting a Pre-Treatment Method

The influence of the calcination process on the physicochemical properties and catalytic behavior of the Co/Mg/La catalysts for ammonia synthesis has been investigated. The catalysts were prepared using the different thermal pre-treatment methods prior to the activation, i.e., drying and calcination, and the respective activities for ammonia synthesis were assessed. It was found out that changing from air calcination prior to activation to direct activation of the co-precipitated species led to the different catalytic performances. The most favorable catalytic performance was achieved with Co/Mg/La prepared by calcination in air. Detailed characterization methods, employing e.g., XRPD, H2-TPD, N2-TPD, CO2-TPD, SEM, and TEM, showed that the superior catalytic behavior of this catalyst was attributed to its strong basicity and favorable adsorption properties toward hydrogen and nitrogen.

A high performance barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide for ammonia synthesis

Ammonia synthesis was performed over a barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide. The rate of NH3 formation over this catalyst was about 3.5 times higher than that over the unpromoted catalyst at 9 MPa and 400 °C. Furthermore, no sign of thermal deactivation was observed during long-term overheating at 600 °C for 360 h. The results of physicochemical studies, including XRPD, DRIFTS, H2-TPD, CO2-TPD, Nads + H2 TPSR and kinetic analysis, revealed that the addition of Ba promoter increased the surface basicity of the catalyst and modified the adsorption properties of the Co surface towards H2 and NH3. The decreased adsorption strength of the corresponding sites towards hydrogen and ammonia resulted in greater availability of active sites in the Ba-promoted cobalt catalyst. These characteristics are considered to have a profound effect on the performance of this catalyst in NH3 synthesis.

Applications of rare earth oxides in catalytic ammonia synthesis and decomposition

Due to their unique structural and electronic properties, rare earth oxides have been widely applied as supports and promoters in catalytic ammonia synthesis and decomposition.

Enhanced ammonia synthesis performance of ceria-supported Ru catalysts via introduction of titanium

The spatial arrangements of Ti species would affect the electronic metal-support interactions and the proportion of Ce3+ sites for ceria-supported Ru catalysts. Ti-Surface-loaded CeO2 supported Ru catalysts exhibited excellent ammonia synthesis activity, which is attributed to a larger proportion of Ru metal, more electrons of Ru species and better adsorption ability of hydrogen and nitrogen.

Efficient ammonia synthesis over a core–shell Ru/CeO2catalyst with a tunable CeO2size: DFT calculations and XAS spectroscopy studies

In the present work, Ru@CeO₂catalysts similar in their core–shell morphology but different in nanoparticle sizes (95, 150 and 225 nm) were obtained by varying the hydrothermal time for the preparation of colloidal carbon spheres to be used as templates.

Efficient ammonia synthesis over a Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at high temperature

A Ru/La_0.5Ce_0.5O_1.75 catalyst pre-reduced at an unusually high temperature (650 °C) catalyses ammonia synthesis at a high rate under mild conditions.

Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber–Bosch process, consumes a huge amount of energy; therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La_0.5Ce_0.5O_1.75 pre-reduced at an unusually high temperature (650 °C) catalysed ammonia synthesis at extremely high rates under mild conditions; specifically, at a reaction temperature of 350 °C, the rates were 13.4, 31.3, and 44.4 mmol g^–1 h^–1 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning under the conditions tested. Electron energy loss spectroscopy combined with O₂ absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter < 2.0 nm) that were partially covered with partially reduced La_0.5Ce_0.5O_1.75 and were dispersed on a thermostable support. Furthermore, Fourier transform infrared spectra measured after N₂ addition to the catalyst revealed that N₂ adsorption on Ru atoms that interacted directly with the reduced La_0.5Ce_0.5O_1.75 weakened the N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst, which consists of Ru supported on a thermostable composite oxide with a cubic fluorite structure and containing reducible cerium, resulted in the formation of many sites that were highly active for N₂ reduction by hydrogen.

New insights into the support morphology-dependent ammonia synthesis activity of Ru/CeO2catalysts

Different morphologies ceria (nanocubes, nanorods and nanoparticles) were synthesized and exhibited significant support-morphology-dependent catalytic activity towards ammonia synthesis.